2018 Humming Noise 35mph, lemon? - Jeep Compass Forum
 
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post #1 of 23 Old 06-04-2018, 11:59 PM Thread Starter
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2018 Humming Noise 35mph, lemon?

Hey guys, have about 5500 miles on the 2018 Compass 4WD and at about 30-35mph there’s a humming noise from under the vehicle - sounds like it’s from the transmission or differential.

The noise goes away as soon as you slow down, accelerate, or switch the gear shifter into the tiptronic mode. I’ve been doing some reading online and it seems like a lot of people aren’t having issues with this and either there’s no fix or are being told it’s normal.

Here’s another thread about the issues:

http://www.myjeepcompass.com/forums/...s/37538?page=3

Now my question is, has anyone thought of or tried to pursue any sort of lemon law settlement related to this?

Doesn’t seem to me like a humming noise would be normal as it does get quite annoying if you’re doing that speed for a little while.
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post #2 of 23 Old 06-05-2018, 07:20 AM
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Hello,

There is a lot of post about this problem.
I have the same problem on my 4x4 2018 compass, It's a loud humming about 30 - 35mph.
I think nobody knows if it's normal or not and the problem has begun on the Renegade 3 or 5 years ago and there is no fix at these day and they continue to made car with this problem ???

Sorry fot my bad english
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post #3 of 23 Old 06-05-2018, 03:33 PM
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Why would you go through the effort of finding an existing thread on and issue, and then create a new thread instead of posting in the existing one?

You know whats worse than that even, in the same thread you linked to the second to last post has your answer. Jeep has spoken on this issue by way of bulletin and essentially clarified that it is not an issue at all. This is just a noise these vehicles occasionally make due to design of the drivetrain.

Here is yet another thread you could have searched for or posted in:
Post -> http://www.myjeepcompass.com/forums/...tml#post133529

You can't bring legal action against a perfectly functioning car that has nothing wrong with it and is working as designed. Thats as silly as saying
Quote:
Hey guys, I noticed there is this metal pipe at the back of my vehicle. When the engine is running there is some hot air and smoke and noise that comes out of it. Its like, barely noticeable, but I don't feel like this is normal. Has anyone else gone to their dealer and complained about this?
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post #4 of 23 Old 06-05-2018, 06:14 PM Thread Starter
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My post wasn’t really about the issue as I know it’s there, it’s more about legal action for it since there is no fix for a known issue.

And your reasoning isn’t really valid because it isn’t perfectly functioning, the noise wasn’t there from 100 to about 4000 miles of owning it, it just started within the last 1000-1500 miles.

Quote:
Originally Posted by arudlang View Post
Why would you go through the effort of finding an existing thread on and issue, and then create a new thread instead of posting in the existing one?

You know whats worse than that even, in the same thread you linked to the second to last post has your answer. Jeep has spoken on this issue by way of bulletin and essentially clarified that it is not an issue at all. This is just a noise these vehicles occasionally make due to design of the drivetrain.

Here is yet another thread you could have searched for or posted in:
Post -> http://www.myjeepcompass.com/forums/...tml#post133529

You can't bring legal action against a perfectly functioning car that has nothing wrong with it and is working as designed. Thats as silly as saying
Quote:
Hey guys, I noticed there is this metal pipe at the back of my vehicle. When the engine is running there is some hot air and smoke and noise that comes out of it. Its like, barely noticeable, but I don't feel like this is normal. Has anyone else gone to their dealer and complained about this?
[IMG class=inlineimg]http://www.myjeepcompass.com/forums/images/smilies/Smileys/Smiley Nose Pickin.gif[/IMG]
[IMG class=inlineimg]http://www.myjeepcompass.com/forums/images/smilies/New/pat.gif[/IMG]
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post #5 of 23 Old 06-05-2018, 07:56 PM
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Au contraire, you are still a newb with less than 10k miles on your Jeep but if you dig and do your homework and keep driving it you will soon learn just how thoroughly beaten to death this horse is.

You may not have noticed the sound up to this point, doesn't mean it was not there. Its terribly subtle but once you do start noticing it you become more and more sensitive to it. You either did not notice it before, or it was inapplicable due to the weather/season you were driving in (ie, Winter when the vehicle tends to stay in all-wheel mode much moreso than the warmer months). The exact conditions that allow for the sound can be difficult to reproduce because it is a culmination of a lot of variables.

Its just a sound these things sometimes make. The 4x4 Renegades have had it since day one, thousands upon thousands of them racking up oodles of miles (they have been out a couple years longer than the 2nd gen Compasses) and despite the noise they are all still working just fine. Car magazines and reviewers have blogged about it, countless forum goers have mused about it, adamant people have thrown tantrums at dealers until half of their drivetrain has been replaced and still, the noise always persists.

The official word on it from FCA suggests the engineers are attempting to mitigate the noise through software but I'm sure this is a low priority item for them. You can read the STAR document here: http://www.myjeepcompass.com/forums/133521-post19.html

I am highly suspicious of this "software update", about the only way it could possibly help is by compromising the behavior of the 4x4 system in some way so assuming they give me the option I'd rather have it make an occasional sound than give up something from the clever automatic system they built which, in my opinion, works very well at both promoting best possible traction and peak efficiency.

Either way, you have nothing to stand on for legal action. People can point to 4-year old Renegades with 100,000+ miles that run perfectly and still make the sound to this day, it is not an indication of any type of actual problem whatsoever. Just an operating noise indicating your highly advanced 4x4 system is doing its best for you.
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post #6 of 23 Old 06-05-2018, 08:27 PM
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Quote:
Originally Posted by arudlang View Post
Au contraire, you are still a newb with less than 10k miles on your Jeep but if you dig and do your homework and keep driving it you will soon learn just how thoroughly beaten to death this horse is.

You may not have noticed the sound up to this point, doesn't mean it was not there. Its terribly subtle but once you do start noticing it you become more and more sensitive to it. You either did not notice it before, or it was inapplicable due to the weather/season you were driving in (ie, Winter when the vehicle tends to stay in all-wheel mode much moreso than the warmer months). The exact conditions that allow for the sound can be difficult to reproduce because it is a culmination of a lot of variables.

Its just a sound these things sometimes make. The 4x4 Renegades have had it since day one, thousands upon thousands of them racking up oodles of miles (they have been out a couple years longer than the 2nd gen Compasses) and despite the noise they are all still working just fine. Car magazines and reviewers have blogged about it, countless forum goers have mused about it, adamant people have thrown tantrums at dealers until half of their drivetrain has been replaced and still, the noise always persists.

The official word on it from FCA suggests the engineers are attempting to mitigate the noise through software but I'm sure this is a low priority item for them. You can read the STAR document here: http://www.myjeepcompass.com/forums/133521-post19.html

I am highly suspicious of this "software update", about the only way it could possibly help is by compromising the behavior of the 4x4 system in some way so assuming they give me the option I'd rather have it make an occasional sound than give up something from the clever automatic system they built which, in my opinion, works very well at both promoting best possible traction and peak efficiency.

Either way, you have nothing to stand on for legal action. People can point to 4-year old Renegades with 100,000+ miles that run perfectly and still make the sound to this day, it is not an indication of any type of actual problem whatsoever. Just an operating noise indicating your highly advanced 4x4 system is doing its best for you.
Remind me not to piss you off.
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post #7 of 23 Old 06-05-2018, 09:36 PM
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Well I know I should be nicer about it and I apologize for being a prick, I'm just a little exasperated that this keeps coming up.
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post #8 of 23 Old 06-08-2018, 03:19 PM Thread Starter
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I guess I have to live with the fact that I bought a piece of **** that makes noise when driving? I thought other car brands were bad boy I was wrong, at least they don’t have bad wheel bearing noises all day long and say it’s normal.
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post #9 of 23 Old 06-08-2018, 06:09 PM
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I'm not so sure about the "no fix for this issue". If you read through enough Renegade forums you will find a fix was issued for them on this issue. It was replacement of the rear PTU. But this was hit or miss and it seems those that had the entire rear differential unit replaced had the best luck with getting rid of this noise permanently.

Ours has been acting very crazy as of lately as the noise comes and goes sporadically. I have even had the cruise set at 35 MPH and the noise start for a moment then stop with me doing nothing to make it stop. Then we might not hear it again for a week. Then it might be constant for a day or two then go silent for a while again.

We will be due for an oil change soon and I ask the service department to take it for a spin and hope they get lucky enough to hear it. I'm also going to ask them to check all the bolts and mounts having anything to do with the rear differential.

I can't help but to wonder with the replacement of the rear PTU and or differential being such a hit and miss fix along with fact many do not ever develop this noise if this is not an install issue. Something going on with the alignment of these parts or even the mounting them. Bolts that might be too tight,too loose or issue with isolating mounts. One of my thoughts would be something that should be stopping vibration/noise from being transmitted into the cabin might be the problem. Anyone that has ever driven a vehicle with solid engine mounts would know what I'm talking about here.

The thought came to me while driving like 6 miles of 35 MPH zone and the noise competing with the radio. I remembered we had a used mini van that had almost the identical noise and vibration except every now and then I would feel a sharp ping. I got if for a deal so not a huge thing as it had a few other issues as well. I was changing the oil and checking things out underneath and the problem was staring me in the face. It had broken the transmission mount and someone put 4 big band clamps over the top of the mount and around the transmission crossmember. While this did stop the transmission from moving around it also transmitted normal driveline vibrations into the frame where they found their way into the cabin. The cabin acted like a sound box amplifying the noise. I replaced the trans mount along with the engine mounts and the thing turned into a pretty smooth ride.

I would say to anyone having this issue constantly to take your Jeep to the sevice department and have it at least documented. I wish I had done so when the noise was being constant now I have to hope it shows up when I take it in. If there is no noise there is nothing to troubleshoot or document.

Something I do intend to point out is the fact this noise is loud enough at times that I'm turning off the ESC to make it stop and I'm not the only Jeep owner doing this to make the vehicle bearible to drive.The fact we are having to resort to turning off a safety feature to be able to get away from this noise is inexcusable and bound to get someone's attention. Yes we could also switch to 4wd lock but this creates another issue will fuel mileage along with extra wear if you forget shift out of 4wd lock everytime you pass 40 MPH for your whole trip. Turn off the ESC and it's done for your whole trip just hope you don't need the ESC to operate at full capacity. So this could elevate this to being a safety issue.
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post #10 of 23 Old 06-08-2018, 09:04 PM
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Can anyone help? I've been scouring the forums and can't find a place to start. I'm getting a P1729 Transmission code on my 2012 Jeep Compass Latitude 2.4 L 4x4. It was whining and not able to function when in overdrive, at 45 mph it loses power, but if I let it cool for a few and start it back up its fine for a while, then does it again. I read on a few forums it could be a snap ring issue and found shavings in the transmission pan when I drained the fluid. Has anyone else had this issue and what was your resolution?
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post #11 of 23 Old 06-08-2018, 11:01 PM
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Quote:
Originally Posted by Chris Jacobs
If you read through enough Renegade forums you will find a fix was issued for them on this issue. It was replacement of the rear PTU.
Could you provide a link to this? I have read most of the Renegade content I could find on the matter, I saw that some have had the RDM replaced (and either still had the sound or dropped off the map). I don't remember reading about anyone getting the PTU replaced up front but would be interesting to read. We still have the STAR document here (S1503000001) stating that the sound comes from the RDM (not the PTU) and that replacement of the unit is not a fix.

Quote:
Originally Posted by Chris Jacobs
Something I do intend to point out is the fact this noise is loud enough at times that I'm turning off the ESC to make it stop and I'm not the only Jeep owner doing this to make the vehicle bearible to drive.The fact we are having to resort to turning off a safety feature to be able to get away from this noise is inexcusable and bound to get someone's attention. Yes we could also switch to 4wd lock but this creates another issue will fuel mileage along with extra wear if you forget shift out of 4wd lock everytime you pass 40 MPH for your whole trip. Turn off the ESC and it's done for your whole trip just hope you don't need the ESC to operate at full capacity. So this could elevate this to being a safety issue.
Disabling a safety feature just to avoid the possibility of hearing a noise that Jeep has officially declared to be a normal operating sound is an astoundingly foolish notion, on multiple levels. Don't do this.

First off, you apparently don't realize that turning off ESC leaves you locked in AWD. Thats why you don't hear the noise, no switching in and out of 2-wheel drive. Hence its the same effect as hitting the 4x4 button except that turning off ESC additionally disables multiple safety systems, which is bad. So don't turn off ESC, just hit 4x4.

I imagine you are going to be confused by that as well, so as a reminder, this is not a "real" 4x4 vehicle. Its a part-time-all-wheel-drive vehicle based on a front-wheel drive platform with disconnecting rear axle. There are no locks or limited slip devices in the differentials, no transfer case, etc meaning there is no harm in driving around in full-time AWD. 4x4 is stamped all over just because it "sounds more legit" and its not completely inaccurate to say its a "4x4" but only if you flex the definitions of what it means to have a 4x4 vehicle.

There is no additional wear you can measure if you drove it every day in "4x4 Lock". Its already functioning in AWD the majority of the time and you would be completely oblivious to that fact had they not decided that the humming of being in 2WD was an acceptable side effect when they designed the driveshaft disconnects. It starts and operates mostly in AWD from stops and at low speeds, it really only tends to disconnect the rear axle at speeds above 40 depending on the conditions (although I have caught mine in 2WD once at low speed now that the weather is much warmer). Its also locked in AWD when it autostick mode. You can drive in autostick mode 100% of the time, no problem mechanical-wear speaking, and therefor you can drive in AWD 100% of the time too.

Moving on to the last point of why turning ESC off to avoid the sound is stupid...

You can't possibly tell me that as a normal, sane person who cares about whether he and his passengers live or die, that you would rather disable a safety feature than loose 1-2 measly MPGs???

I mean, especially now that you know its IN all-wheel-drive when you turn off ESC anyways... but even when you thought it wasn't... you'd rather save a measly nickel in fuel vs leaving the flipping life-saving safety features on? You are on your own planet dude.

These things are brand new. We've all got gobs of warranty left. If I'm wrong and the rear differentials are going to start failing on us left and right, so what? It will be recalled, and fixed under warranty. Even if it takes a while, as long as its a consistent failure they will have to make it right, just like Nissan was forced to on their horrible CVT transmissions from earlier in the decade. But for cripes sake, NONE, ZERO, ZIP, NOT ONE of these damn things have failed yet. Nobody has been stranded on the side of the road from this sound. Not a single vehicle. Not any of the Renegades, not any of our new Compasses, so until this is demonstrated to be an actual issue, something other than a sound you don't like to hear, DO NOT disable the safety features of your friggin car to try to avoid it.

I'm not big on telling people how to live their lives. I cheer for many of the daily Darwin awards that go out, but for Pete's sake... there are better ways to get FCA's attention to tell them you don't like the sound than rolling your car and dying in it.
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post #12 of 23 Old 06-09-2018, 02:59 AM
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Quote:
Originally Posted by arudlang View Post
Could you provide a link to this? I have read most of the Renegade content I could find on the matter, I saw that some have had the RDM replaced (and either still had the sound or dropped off the map). I don't remember reading about anyone getting the PTU replaced up front but would be interesting to read. We still have the STAR document here (S1503000001) stating that the sound comes from the RDM (not the PTU) and that replacement of the unit is not a fix.



Disabling a safety feature just to avoid the possibility of hearing a noise that Jeep has officially declared to be a normal operating sound is an astoundingly foolish notion, on multiple levels. Don't do this.

First off, you apparently don't realize that turning off ESC leaves you locked in AWD. Thats why you don't hear the noise, no switching in and out of 2-wheel drive. Hence its the same effect as hitting the 4x4 button except that turning off ESC additionally disables multiple safety systems, which is bad. So don't turn off ESC, just hit 4x4.

I imagine you are going to be confused by that as well, so as a reminder, this is not a "real" 4x4 vehicle. Its a part-time-all-wheel-drive vehicle based on a front-wheel drive platform with disconnecting rear axle. There are no locks or limited slip devices in the differentials, no transfer case, etc meaning there is no harm in driving around in full-time AWD. 4x4 is stamped all over just because it "sounds more legit" and its not completely inaccurate to say its a "4x4" but only if you flex the definitions of what it means to have a 4x4 vehicle.

There is no additional wear you can measure if you drove it every day in "4x4 Lock". Its already functioning in AWD the majority of the time and you would be completely oblivious to that fact had they not decided that the humming of being in 2WD was an acceptable side effect when they designed the driveshaft disconnects. It starts and operates mostly in AWD from stops and at low speeds, it really only tends to disconnect the rear axle at speeds above 40 depending on the conditions (although I have caught mine in 2WD once at low speed now that the weather is much warmer). Its also locked in AWD when it autostick mode. You can drive in autostick mode 100% of the time, no problem mechanical-wear speaking, and therefor you can drive in AWD 100% of the time too.

Moving on to the last point of why turning ESC off to avoid the sound is stupid...

You can't possibly tell me that as a normal, sane person who cares about whether he and his passengers live or die, that you would rather disable a safety feature than loose 1-2 measly MPGs???

I mean, especially now that you know its IN all-wheel-drive when you turn off ESC anyways... but even when you thought it wasn't... you'd rather save a measly nickel in fuel vs leaving the flipping life-saving safety features on? You are on your own planet dude.

These things are brand new. We've all got gobs of warranty left. If I'm wrong and the rear differentials are going to start failing on us left and right, so what? It will be recalled, and fixed under warranty. Even if it takes a while, as long as its a consistent failure they will have to make it right, just like Nissan was forced to on their horrible CVT transmissions from earlier in the decade. But for cripes sake, NONE, ZERO, ZIP, NOT ONE of these damn things have failed yet. Nobody has been stranded on the side of the road from this sound. Not a single vehicle. Not any of the Renegades, not any of our new Compasses, so until this is demonstrated to be an actual issue, something other than a sound you don't like to hear, DO NOT disable the safety features of your friggin car to try to avoid it.

I'm not big on telling people how to live their lives. I cheer for many of the daily Darwin awards that go out, but for Pete's sake... there are better ways to get FCA's attention to tell them you don't like the sound than rolling your car and dying in it.

Quote:
Originally Posted by arudlang View Post
Could you provide a link to this? I have read most of the Renegade content I could find on the matter, I saw that some have had the RDM replaced (and either still had the sound or dropped off the map). I don't remember reading about anyone getting the PTU replaced up front but would be interesting to read. We still have the STAR document here (S1503000001) stating that the sound comes from the RDM (not the PTU) and that replacement of the unit is not a fix.



Disabling a safety feature just to avoid the possibility of hearing a noise that Jeep has officially declared to be a normal operating sound is an astoundingly foolish notion, on multiple levels. Don't do this.

First off, you apparently don't realize that turning off ESC leaves you locked in AWD. Thats why you don't hear the noise, no switching in and out of 2-wheel drive. Hence its the same effect as hitting the 4x4 button except that turning off ESC additionally disables multiple safety systems, which is bad. So don't turn off ESC, just hit 4x4.

I imagine you are going to be confused by that as well, so as a reminder, this is not a "real" 4x4 vehicle. Its a part-time-all-wheel-drive vehicle based on a front-wheel drive platform with disconnecting rear axle. There are no locks or limited slip devices in the differentials, no transfer case, etc meaning there is no harm in driving around in full-time AWD. 4x4 is stamped all over just because it "sounds more legit" and its not completely inaccurate to say its a "4x4" but only if you flex the definitions of what it means to have a 4x4 vehicle.

There is no additional wear you can measure if you drove it every day in "4x4 Lock". Its already functioning in AWD the majority of the time and you would be completely oblivious to that fact had they not decided that the humming of being in 2WD was an acceptable side effect when they designed the driveshaft disconnects. It starts and operates mostly in AWD from stops and at low speeds, it really only tends to disconnect the rear axle at speeds above 40 depending on the conditions (although I have caught mine in 2WD once at low speed now that the weather is much warmer). Its also locked in AWD when it autostick mode. You can drive in autostick mode 100% of the time, no problem mechanical-wear speaking, and therefor you can drive in AWD 100% of the time too.

Moving on to the last point of why turning ESC off to avoid the sound is stupid...

You can't possibly tell me that as a normal, sane person who cares about whether he and his passengers live or die, that you would rather disable a safety feature than loose 1-2 measly MPGs???

I mean, especially now that you know its IN all-wheel-drive when you turn off ESC anyways... but even when you thought it wasn't... you'd rather save a measly nickel in fuel vs leaving the flipping life-saving safety features on? You are on your own planet dude.

These things are brand new. We've all got gobs of warranty left. If I'm wrong and the rear differentials are going to start failing on us left and right, so what? It will be recalled, and fixed under warranty. Even if it takes a while, as long as its a consistent failure they will have to make it right, just like Nissan was forced to on their horrible CVT transmissions from earlier in the decade. But for cripes sake, NONE, ZERO, ZIP, NOT ONE of these damn things have failed yet. Nobody has been stranded on the side of the road from this sound. Not a single vehicle. Not any of the Renegades, not any of our new Compasses, so until this is demonstrated to be an actual issue, something other than a sound you don't like to hear, DO NOT disable the safety features of your friggin car to try to avoid it.

I'm not big on telling people how to live their lives. I cheer for many of the daily Darwin awards that go out, but for Pete's sake... there are better ways to get FCA's attention to tell them you don't like the sound than rolling your car and dying in it.

I swear dealing with fanboys is impossible! LOL In on of the threads you linked to above in a Renegade forum a FCA official "Jeep Cares" stated the fix was to replace the RDM Sorry said PTU before. Directly under that a person posted a complete differential replacement was required when this work was being done because of metal shavings. This person had been some thousands of miles past this work being done without further issue.

Jeep Renegade Forum - View Single Post - Grinding/vibration/rumble Noise at ~30mph

Jeep Renegade Forum - View Single Post - Grinding/vibration/rumble Noise at ~30mph

FCA still knows this is an issue and is still throwing parts at it to try to solve the issue!

http://www.myjeepcompass.com/forums/132457-post15.html

In this case the fix did not work.

I hate to break it to you arudlang but the fact that most of these Compasses are not being affected by this means the ones that are have something wrong with them period! I don't buy this being normal operation especially since it is clear they are still replacing parts due to this noise. We will see what is said or done once I get my service department to hear what is going on.
Also I don't think anyone expects to end up with a different vehicle than the one that actually test drove. The one you test drive that is nice,relatively quiet then at less than 5k on the OD have the thing start with this crazy sound. If someone test drives one of these in town at 35 MPH and it was making this noise most would drive it back to the dealership and run away as fast a possible. Then find any number of brands of suvs THAT DON'T MAKE THIS NOISE and because of that fact alone are more pleasurable to own.

I will also fill you in on something else yes these Jeeps have a real 4WD system. Technically they are a automatic 4wd with a 4wd driver control and AWD ability.This is why they are marketed as 4WD and not AWD. They simply are not an on demand part time 4WD that many think about when they think 4WD. Like I posted before I'm no greenhorn to any of these systems 4WD,Auto 4WD or AWD which is why this noise bothers me. Want to make a old Subaru make some very similar complaining put a tire on any one axle that is 1-2 inches different diameter. BTW, Something else you will doing after any long driving like this IS REPAIRING YOUR AWD SYSTEM. Yes the new Compass is still under warranty so if it breaks they fix. But again is wear being done to parts that will fail out of warranty?

I also would not be so sure what happens when the ESC is turned off. I like you thought it engages the 4WD lock till I started paying attention to how the Jeep feels with it turned off and watched the MPG gauge. With ESC turned on the Compass starts to feel heavy on twisty mountain roads. Turn the ESC off and you get a much lighter feel. Higher speed enguagement of 4WD lock shows slight drop in MPG turning off the ESC does not have this effect. Also in 4WD lock more wear is in fact being done on parts that are designed to stop spinning or working when the vehicle would normally operate in 2wd mode. As far as I can see the only things spinning on the rear in 2WD mode is the wheel bearings,CV shaft and CV shaft support bearing. Versus 4WD lock where the whole rear diff is spinning,the drive shaft.drive shaft support bearings and part of the PTU in the transmission that might not be in 2WD mode. That is a lot of parts added to the mix in 4WD. Seems FCA engineers looked at all that drag which is also extra wear and decided to disconnect them for good reason.

I now believe turning the ESC is not turning the 4WD on but instead changing the programming and the actuation of parts of the stability system. Something we do know is that hitting the ESC button actually does not totally kill the system. Instead the system gets dialed back which is why I said with it turned off hope you don't need it to work in its full potential. This allows for that lighter feeling and fun factor when tossing it around on loose surfaces but still allows the ESC to limit how out of whack you can get for safe fun. FCA has actually been pretty tight lipped about how the programming of this system works. I do wish they would post a video or some sort of information that digs deeper into how the system works mechanically.

While turning off the ESC is cutting back a bit of safety myself I'm comfortable with it just I should not have to do this and neither should other owners of Jeeps that are doing the same thing. Others might not be comfortable in doing this. However I learned to drive old school no ABS,ESC,TC and whatever else others use to describe all these driver's aid electronic magic. In fact I still drive an 03 Chevy Tracker almost daily that has none of this stuff on it not even ABS and over 10 years of owning it not only have I survived I have never been in a situation where I missed any of it. We also have an 04 4x4 Suburban that only has ABS. Neither one is a problem for my wife and I to drive. But again the wife like myself learned to drive old school. Heck the cars we learned to drive still had this old time fuel delivery system called a carburetor you might have heard about those maybe. lol

My point was people doing this to avoid this noise/vibration are in fact being driven to do this by this defect in their Jeep. Without doubt some of them have never driven anything without a full on ESC and traction control so for them this could be a big issue.
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post #13 of 23 Old 06-11-2018, 03:40 PM
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Use your noodle a little bit Chris, lets break this down:

Jeep Renegade Forum - View Single Post - Grinding/vibration/rumble Noise at ~30mph

So on this one in 2015 the Renegade Jeep Cares account said the fix was replacement of the RDM. The problem with this? Its from 2015!

I'll get back to that in a second but you also cherry-pick one post to support your case ( URL="http://www.jeeprenegadeforum.com/forum/416513-post159.html"]http://www.jeeprenegadeforum.com/forum/416513-post159.html[/URL] )
to which I say fine but in the same thread I can cherry pick posts from people for whom the replacement did not work, I'm not going to now because I'm sure you read those and just chose to ignore them, but there are plenty of them there plus the example in our own forum where replacement did not work out for member KAMI_1 as you noted above.

The first part of the problem is there is no expectation that people will be good about going back to those threads and saying "whoops, just kidding, mine has the noise again all of a sudden". If they *think* its gone they will relax, turn up the radio and quit listening probably, or just give up altogether.

The much more substantial problem is the posts in that thread are very old, the latest STAR document we are aware of (S1503000001) is marked as a REVISION to an existing case, and states the dealers should remove all previous copies from their files. Now I don't think they actually give the case number in the Renegade thread so I can't say for certain its the same case but likely it is, or its the Compass version of the exact same case, and the LATEST document has backpedaled on the RDM replacement and now says "do not replace the RDM... Engineering is working on a software update to reduce it"

So, maybe back in 2015 when the Renegades were initially discovering the sound there may have been a bunch of (mostly unsuccessful) RDM replacements but they have obviously now figured out replacing that part doesn't help, because its a design characteristic.

Moving on, I don't believe you have sufficient evidence to assert that most Compasses are not affected. Going on 100,000 of these new models have been sold, you and I do not have anywhere near a sufficient sample to make claims about how many of the 4x4 ones produce this sound.

Moving further down your response... you are lost in the woods at "since it is clear they are still replacing parts due to this noise". No they are not. In 2015 they were replacing parts, sure, they are not replacing them now as far as we can see.

Your concern that the noise doesn't start in until 5k doesn't hold water with me. Its entirely possible that either A) you didn't hear it, or B) seasonal conditions reduced the scenario that creates the noise for you initially, or C) it took some miles for the transmission control module learning to tweak parameters into a range that creates the sound more often, or D) a combination of any or all of the above. At any rate, mine did it from within the first 100 miles, its still doing it today (and still running and driving great).

Other brands don't make this noise because most don't have a part-time system. They are mainly full-time AWD.

You are still misinformed about the AWD/4x4 nature of this vehicle. "4x4" is a marketing tool with a broad definition that includes pretty much any form of AWD system. Our cars are only "4x4" by the LOOSEST of those definitions, and they are NOT the same as a 4x4 system that is comprised of a longitudinal engine RWD platform with a transfer case and front differential that is separate from the transmission. These are front wheel drive transaxle cars with a part-time rear axle, pretty much your quintessential all-wheel-drive. Again, there are no differential locks and the front wheels do the vast majority of the work almost all the time, you could drive one of these in "4x4 Lock" every day for the vehicle's whole life and nothing would be bothered other than your highway mileage would be a tad lower than it could be.

Lets see, then you have a bunch of comments on ESC, those are basically all based on your personal experience and opinion since you don't have any sources to back up how you seem to *think* the system works, so I can safely (dis)regard those comments with all the grains of salt they deserve... Sorry but I don't believe that monitoring estimated fuel economy is a valid indicator of when the vehicle is in 2x4 mode.

I don't get what you think it does different with ESC off, the ONLY thing that prevents this sound is by forcing the vehicle to stay in AWD. It may still be varying the amount of power being sent rearward until its close to nothing (there is a wet clutch back there) but something stays engaged full-time that would otherwise be free-wheeling and presumably making the sound you dread so much.

We can debate this topic for the life of the vehicles but every day that you and I drive ours to work successfully is another point for the "its not an issue" side. You say its going to fail eventually, well, literally everything on a vehicle is going to fail eventually. The factory powertrain warranty is 5 years/60k miles. This would have been shown to you in no uncertain terms prior to you purchasing the vehicle, and it is on par with many other brand's warranties. They literally only promise 60k miles or 5 years worth, thats all. Thats not new news to anyone. You acknowledged this when you bought it. If you are under some impression that its supposed to last longer than that with no major service, you are pulling that idea out of thin air because we all know in black and white that Jeep only promises and expects the car to give you 5 years or 60k miles worth of relatively trouble-free service, and every mile after that is just a gift.

It sucks to put it that way, but they are a for-profit company just like all the others. They don't want to sell you a 10-year car, they need you to buy a new one in 2-3 years, 5 at most. Its not just Jeep. Things are not built like they used to be. We collectively shake our fists and demand more car for less money, this is what we get.

These buggies are here for a good time, not a long time.
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post #14 of 23 Old 06-14-2018, 07:42 PM
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Quote:
Originally Posted by arudlang View Post
Use your noodle a little bit Chris

Use my noodle is laughable coming from a person that has no clue as to the type of drive system his Jeep even has but has insisted on trying to tell me and others what is or is not normal for the vehicle. We will get more into this later!

Fact the Compass is pretty much a Renegade with a different body shape. Fact Jeep acknowledges that some of these vehicles are in fact making a noise that is not normal. Fact on this forum alone at least 2-3 people have had parts replaced because of this noise. Fact the 2nd Gen Compass did not even start it's run till mid to late 2017 that means the noise is still being addressed by Jeep within the year. Fact one member here reported RDU replacement very currently. So yes even at this point Jeep is chasing this issue. Fact I truthly don't know how this issue will be resolved till I get our Jeep in at a time the noise can be heard and documented so I'm not getting overly concerned yet.

Now for facts about this noise your missing or ignoring. Fact yes temps below 40* put the system in a mode where the noise disappears. Fact it was above this temp on a bright sunny day when I took our Compass for a test drive. Fact the noise was not present at that time. Fact in any conditions or temperature above 40* the noise may or may not be present. It can not be there then stop at a redlight take back off and end up with the noise and temp or road conditions remained unchanged in those few moments. Plain and simple this is a defect it does not really matter how many units are effected as we have seen from history every unit in a run can be effected by a defect just look at the the whole Takata airbag mess. Fact given the nature of people to complain on the internet it is safe to assume not all Compass and Renegade with 2.4 autos are effected by this noise. Again meaning the ones that are are suffering from a defect.

Turning off the ESC, Your right I'm not 100% certain exactly what all mechanically and electronically is happening as FCA has not explained exactly what what is going on with the system when the switch is flipped. So we have to rely on our experience both as a mechanic and an experienced driver of 4WD and AWD vehicles. Yes fuel consumption changes tell you a lot. One thing is about changes in friction in the vehicle. There is a very big reason these Jeeps shift into a 2wd mode and that is to save fuel. There is also reason why these Jeeps even go a far as to disconnect the rear drive shaft at both ends again to save fuel. So observing fuel use help us make an educated guess at what is going on with the ESC turned off/muted vs shifting into 4WD lock.

How the vehicle feels is another good indicator as to how the system is working. But to really pick up on it you do need to develop a sense of how the drivetrain is working. My sense of this is pretty darn good as I can tell within minutes of driving if I forgot to unlock or lock my hubs on my Tracker or my Ranger even with them in 2wd. The Jeep gets a heavier steering feel in sharp curves and corners when it is switched into 4wd lock that is not there when the ESC switch is off in normal driving or in other words not pushing it performance wise. This indicates it is putting more power to the rear.

I have been constantly looking for anything that shows mechanically how the system works. Last night I ran across something on the Fiat/renegade 4wd system that clears the water a bit. It seems that when these systems are left in auto mode and speed is 40 MPH or less in good conditions they are in fact operating in a front drive biased all wheel drive mode. What is going on is is pretty simple power is being sent to both axles with the front receiving the most. Then if the front starts to slip or sensors indicate the vehicle may need more traction in the immediate future more power is sent to the rear. From there the system will move power around as needed till the vehicle is stabilized then it goes back to a front biased AWD. This is no big surprise to me because in full auto mode the Jeep is lighter in the steering until pushed in the corners then it gets a bit heavy.

Now this is the tricky bit and while it seems the same to those not fully understanding how these systems work it might seem to the the same difference just coming from a different way when in fact that is way off. When the 4wd lock is selected the front PTU locks. This splits the power 50/50 front and rear from the start so the front bias no longer exist. This causes more fuel use and heaver feel in the steering. Now instead of moving power to the rear the system is free to juggle the power front to rear as needed but wants to maintain 50/05 split when not moving power around. So yes I am correct as far as shifting to 4wd lock. My guess is that what is happening to stop the noise when ESC is turned off it that either the system is keeping the drive shaft either fully engaged or fully disengaged. Alternatively the issue may be in the ESC system itself and turning it off is muting a part of the system that is causing the noise.

Now let's clear up what type of drive system the little 4WD Jeeps have! All that follows is referring to 4 wheeled vehicles.

Your notion that real 4WD vehicles have to have "a longitudinal engine RWD platform with a transfer case and front differential that is separate from the transmission." is entirely false.

What you are referring to is not a "real 4wd system" it is just a conventional 4wd system. Let's break it down shall we.

The position of the engine has no effect on the 4wd system. Yes it can affect a vehicle's handling but 4wd mechanics are not effected.

A 4wd only needs a means of getting power to both axles how it does this again does not matter so a PTU and a dedicated transfer case make zero difference to the 4wd system. Now you might be screaming about low range. Low range is about gearing not about 4wd. Many 4wd systems even in a conventional layout did not have low range gearing.

The drive platform as far as front or rear again does not affect the ability of 4wd. The system performs the same whether normal operating mode is front or rear dive. Again vehicle manners are different but mechanically still 4wd.

Now let's break things down to reality. What goes into naming/identifying different drive types found in the passenger vehicle industry.

2wd pretty simple 4 wheel vehicle with only 2 wheels on a common axle receiving power.

4wd thing get a little crazy because there are different systems all under 4wd category.

The first I call a pure simple 4wd system. The only mode the vehicle has is to drive all 4 wheels and has no slippage in the drivetrain. As you might guess this is only to be used on surfaces where tires can slip to alvate driveline pressure that will build up and break things if it can't be relieved.

User selectable 4wd again simple vehicle can operate in either 2wd or 4wd depending on what the user chooses.

Auto 4wd. A system that switches itself between 2wd and 4wd as needed.

Now we get a little tricky. Full time 4wd. in their simplest form they are just that. the system stays in 4wd all the time with driveline pressure being relieved by a mechanical device allowing for some slippage between the axles when needed. Again in its simplest form they did not transfer power between the axles just relieve the stress that builds in the system. Later some systems labeled as full time 4wd started to take on some Awd characteristics and could transfer some power between the axles.

Now move to AWD. Again simple power sent to all 4 wheels all the time. The big difference to 4wd is the the system can transfer power depending on traction conditions. The fact that all 4 wheels have to receive power all the time when the system is not transferring power means a AWD vehicle CANNOT HAVE A 2WD MODE!

Now spend some time on youtube watching videos of Jeep Renegades on trail rides with other vehicle types including conventional 4WD rigs. There is one out there that shows a Renegade making short easy work out of a slippery hill that makes Jeep XJs without lockers work for it. Goes to prove these little Jeeps are true 4WD with the heart of a little beast that in some off-road situations can hold their own and even outperform conventional 4wd monsters with lifts and very aggressive big tires. Say thank you to the computer figuring out traction solutions and those brake lock diffs!

Now let's look at our Jeeps. Yes in normal auto mode it starts out in AWD then shifts into a 2wd mode in normal conditions. If we ignore everything else these Jeeps do at worse you have a 2wd with AWD capability because an AWD with 2WD capability is an impossibility given the meaning of AWD.

But that is not all there is. These Jeeps can also automatically or manually be shifted into a true 4wd mode with power being split 50/50 front and rear the fact that it deploys some AWD tech to move power around in some modes does not make it an AWD vehicle and certainly does not make it a fake 4wd. This ability means that 4WD in this case is earned and not just "a marketing tool".

As to operating in 4wd mode all the time and wear well I'll tell you for a fact tires will wear quicker. Anything that does not work in 2WD will also wear quicker. The rate of this wear will depend on it's duty in the system and the quality of the parts and their engineering period! Parts that work wear the more they work the more they wear you in your rant acknowledges this.

Now expected vehicle life and warranty hate to break it to you there as well but your off your mark. Warranty is how far they anticipate faulty parts or workmanship could last. Yes how long something can last is factored in but is not the main factor. Our Suburban I think had a 5/50 or 6/60 on it's powertrain. It had its first major powertrain failure around 200k which was the rear diff. it's 2nd major failure was over 200k which was the transmission. pushing 230k engine still fine! This is very common among Ninth generation Suburbans and many of the GMC truck line made after the late 80s. This also explains why you see so many GM trucks on the road. Most owners figure the brand has earned their loyalty.

Most here in the US veiw any vehicle that has major drivetrain failure before 130k as non-durable and not a good investment. Vehicles that have major failure before 150k are just mediocre. Major failure at or before 60k is a lemon. If these jeep start having major issues constantly before 120k Jeep will be either doomed or yet again needing new ownership. So let's hope whatever this noise is they figure it out and do right by their owners or that it is infact a mostly harmless noise. Keep in mind though given the amount of nice quite 4WD/AWD vehicles out there if it gets out these jeeps have this issue and it is not being fixed FCA will still suffer from the backlash.
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post #15 of 23 Old 06-14-2018, 08:56 PM
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Alright well as usual we have a big conglomerate of assertions and statements, some of them have evidence, some of them are opinion or unfounded, the line between 4x4 and AWD is very blurry these days so we can agree to disagree on some aspects there but you are right in that what I had in mind was "conventional" 4x4 even though I lacked the precise semantics to articulate that. But for the record, putting "fact" in front of every sentence does not make it so.

Anyways I only have a couple things from your post earmarked to touch on:

Quote:
Originally Posted by Chris Jacobs
So observing fuel use help us make an educated guess at what is going on with the ESC turned off/muted vs shifting into 4WD lock.
In a technical sense this would be true but only in a laboratory-type setting where all other conditions and factors can be held constant or accounted for. Dozens, sometimes hundreds of variables are in motion while driving, even on flat ground. Add to that the fact that the dash economy screen readout is a rough estimate, and you essentially have too complicated a system with too blunt of measurements to support your claims. The manufacture of this drive system (which by the way is not jeep) only claims that a 4% improvement in fuel economy is possible with this system. For our application that only translates to about 1 MPG, which is too deep into the margin of error created by driving in dynamic conditions to be able to reliably detect, especially not by a person. If your instant MPG readout goes up by 1 suddenly, you can't know for sure if its because the rear axle disconnected or because a gust of wind is suddenly at your back.

Quote:
Originally Posted by Chris Jacobs
The Jeep gets a heavier steering feel in sharp curves and corners when it is switched into 4wd lock that is not there when the ESC switch is off in normal driving or in other words not pushing it performance wise. This indicates it is putting more power to the rear.
If only we lived closer, I'd love to tape some cardboard over the center of the cluster and the 4x4 button and have you drive around for about 15-20 minutes with me discreetly switching 4x4 on or off at random and have you guess which state it was in throughout the drive, then we'd find out very quickly if you are as perceptive as you think you are...


How about this Chris here is a nice olive branch I'll share with you rather than hoard it to myself, a link to a page of the website of the company that ACTUALLY designed this system in our cars. You will love this, just found it today, tons of detail on the design and function of the system in the Renegade which as you know is essentially the same as what we have in the Compass. Even has a cool video that shows animated renderings of what happens and when inside the PTU and the RDM. If your brain is a sponge for technical information this will be like a bucket of cool water on a hot summer day:
https://www.gkn.com/en/our-divisions...g-experiences/

Neat stuff, right?

Based on this, I assume the reason Jeep reps never have anything useful to tell us about this sound is because they didn't design it, and hence they don't have the answers. They probably (hopefully) have an inquiry out to GKN about it but that is why even if you had a Jeep engineer as a neighbor you would have a hard time getting the scoop because he or she would have to get it from a GKN engineer first. Jeep probably asked GKN to work on a software tweak to the system to mitigate the sound, I would guess. The turnaround time could be a while on that since GKN is also busy doing drive systems for Range Rover and Ford and others...

Anyways now that you have seen some more in-depth info about how the thing works, what do you make of this sound now?

I still think one theory is that the sound is what you get when the system decides to use the variable clutch in the RDM to bring the driveshaft partially or fully up to speed to prepare for (but has not yet made the final decision to) engage the dog clutch in the front.

It could also be something that happens when its trying to go out of 4x4 but perhaps the force being exerted on one engaged part prevents it from immediately "letting go" so something extra is still being spun even though its free to be released the current torque through the wheels or something is helping it hang on.

Or something totally different still.

There is a contact page on GKN's website, perhaps its time to go over jeep's head and try to get some straight answers direct from the source!
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post #16 of 23 Old 06-15-2018, 01:43 AM
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I think we have passed the point of this needing it's own thread. Sorry Sam091990 but as you can see there is a debate on what the deal with this noise is and what Jeep is doing about it. I would say taking FCA to court over this issue on lemon law and what a judge might rule is a crapshoot at best depending on the judge and his mood that day. I will say if the judges car broke down and the only rental/loaner available to him was a Jeep Renegade or Compass with this issue and he had to drive it for 2 weeks in city 30-40 mph traffic your chances will be pretty good. LOL


Quote:
Originally Posted by arudlang View Post
Alright well as usual we have a big conglomerate of assertions and statements, some of them have evidence, some of them are opinion or unfounded, the line between 4x4 and AWD is very blurry these days so we can agree to disagree on some aspects there but you are right in that what I had in mind was "conventional" 4x4 even though I lacked the precise semantics to articulate that. But for the record, putting "fact" in front of every sentence does not make it so.
Again much of my statement is educated guess but everything I stated as saying is a fact is a fact like it or not.


[/QUOTE] In a technical sense this would be true but only in a laboratory-type setting where all other conditions and factors can be held constant or accounted for. Dozens, sometimes hundreds of variables are in motion while driving, even on flat ground. Add to that the fact that the dash economy screen readout is a rough estimate, and you essentially have too complicated a system with too blunt of measurements to support your claims. The manufacture of this drive system (which by the way is not jeep) only claims that a 4% improvement in fuel economy is possible with this system. For our application that only translates to about 1 MPG, which is too deep into the margin of error created by driving in dynamic conditions to be able to reliably detect, especially not by a person. If your instant MPG readout goes up by 1 suddenly, you can't know for sure if its because the rear axle disconnected or because a gust of wind is suddenly at your back. [/QUOTE]

Do not focus on that 4% efficiency loss! This is very much like EPA fuel efficiency numbers. The first thing you need to find out is if this number is real world tested or just a calculation on paper or computer. Next up if numbers have been road tested is what where the conditions of the test. Then which programming was installed when the test was done. Lastly mode of operation the system was tested in. I see where under set conditions how this system might yield losses of only 4%. You will notice at the end of the video it states software is tuned to the brand the hardware is in. Now go look at the fiat 500 system. The selections for the system is auto,sport,rain/snow. This clearly shows the software is tuned heavily towards AWD with the option for a rear wheel drive bias. My guess is this was the set up tested for efficiency most likely with the system active on dry level road at a given speed.

This is going to be very different than the same hardware with software capable of running in a 4wd mode. When the system can be set to 50/50 power split and is capable of being far more aggressive in moving power around. The devil is all in the details.



[/QUOTE]If only we lived closer, I'd love to tape some cardboard over the center of the cluster and the 4x4 button and have you drive around for about 15-20 minutes with me discreetly switching 4x4 on or off at random and have you guess which state it was in throughout the drive, then we'd find out very quickly if you are as perceptive as you think you are...[/QUOTE]

Do us both a favor get out there and have fun with your vehicle's find a safe place and push them to their limits. You should actually do this to anything new you drive just so you know where those limits are in case you need this info to avoid a crash. Then get off road and have some fun. Play with those settings and see what they really do and feel how they work. Drive some different vehicles with different drive types. Something you will learn quickly is the characteristics of different drive types are very different. Pushing an AWD into a corner feels totally different from a front or rear drive vehicle. I would not push a conventional locked 4WD into a corner on pavement but on dirt is fine. Do this with a conventional locked 4WD and with the Compass in 4WD lock and your going to feel the difference. After enough of this someone could cover the 4wd mode and dash on the Compass and you too will know pretty darn much what setting the 4WD is in. LOL




[/QUOTE]How about this Chris here is a nice olive branch I'll share with you rather than hoard it to myself, a link to a page of the website of the company that ACTUALLY designed this system in our cars. You will love this, just found it today, tons of detail on the design and function of the system in the Renegade which as you know is essentially the same as what we have in the Compass. Even has a cool video that shows animated renderings of what happens and when inside the PTU and the RDM. If your brain is a sponge for technical information this will be like a bucket of cool water on a hot summer day:
https://www.gkn.com/en/our-divisions...g-experiences/ [/QUOTE]

I have seen an edited version of this video someplace and it confirmed something I thought which is this system is using wet clutch packs to transfer torque front to rear. No surprise it is one of the common methods to do this job when a system can send 100% power to either axle. I don't think it touched on the dog clutch though so that was interesting tidbit to learn.

[/QUOTE]Neat stuff, right?[/QUOTE] yes it was nice to see the full video. I think we all pretty much knew this drive system is heavily software based.

[/QUOTE]Based on this, I assume the reason Jeep reps never have anything useful to tell us about this sound is because they didn't design it, and hence they don't have the answers.[/QUOTE]

Actually you might be surprised as Jeep may have secured software rights to tweak and work on the software. This is not an uncommon practice.

[/QUOTE]They probably (hopefully) have an inquiry out to GKN about it but that is why even if you had a Jeep engineer as a neighbor you would have a hard time getting the scoop because he or she would have to get it from a GKN engineer first. Jeep probably asked GKN to work on a software tweak to the system to mitigate the sound, I would guess. The turnaround time could be a while on that since GKN is also busy doing drive systems for Range Rover and Ford and others...[/QUOTE]

Very true and this issue may not be present on other vehicles with different software in a sense you would think that would make it easier to figure out but in reality this could also complicate the issue particularly if Jeep has rights to tweak the software. But if the issue is software based either way your looking at a ton of code to find why it is happening. Also as I stated before the issue could be hardware and they are trying to come up with a software fix this could be a challenge to do and still end up with a vehicle performing as it should. Then of course if it is hardware and not doing a lot of damage or wear short term even finding the parts effected could be very difficult. Lastly a defective part may never present itself as defective by failing and instead cause other parts to fail instead. The whole discovery process can be a huge nightmare taking years to figure out. Since this company is dealing with other car makers and doing R&D for their next big thing they do have their hands full and only dedicating a small team to try to help Jeep figure this thing out.

"Anyways now that you have seen some more in-depth info about how the thing works, what do you make of this sound now?"

My feelings as to the noise is unchanged my first thought is this is not a good sound the question I still have is how much wear or damage is being done. This could be barely noticeable or major. I do have a faint feeling still that something might not be doing it's job in isolating drive line noise/vibration from the cabin. If this is the case then no wear or damage is being done other than to the passengers nerves especially the one's nerves that is making the payments!

"I still think one theory is that the sound is what you get when the system decides to use the variable clutch in the RDM to bring the driveshaft partially or fully up to speed to prepare for (but has not yet made the final decision to) engage the dog clutch in the front.

It could also be something that happens when its trying to go out of 4x4 but perhaps the force being exerted on one engaged part prevents it from immediately "letting go" so something extra is still being spun even though its free to be released the current torque through the wheels or something is helping it hang on.

Or something totally different still. [/QUOTE]

If this noise is mechanical in nature (most likely) either of your ideas could be viable either way there is a defect in hardware or software causing the noise as again I don't see this being the norm on either the Compass or the Renegade.

I questioned the system having an issue with clutch over run early on. If power/energy is moving through the drive shaft when it is not suppose to be it could force the clutches to spin when there is not enough force on them to stop them from spinning. I have heard this in other applications where wet clutches lack the proper load on the pressure plates to hold them. It really could be as simple as the dog clutch is not fully disengaging when it should forcing the clutches to basicly rub on their plates. The other way around if the packs in the rear are not kicking the drive shaft loose cleanly energy might be flying back up to the front by the driveshaft causing the dog clutch to bind and making the front PTU clutches over run. Then again as you stated there are a lot of things going on in this system and many of them would be capable of making a noise like this. Believe it or not it could even be the driveshaft itself. If the shaft was balanced with dynamic tension in mind or is out of balance and dynamic tension is forcing it to act balanced then the shaft may vibrate at given speeds if it is spinning freely. Vibration then could be transferred by the center support bearing into the cabin where it starts making noise and may even be amplified by the cabin itself.

As you can tell I have put a lot of thought into this not because I'm obsessed with it but because I suffer from pretty bad insomnia and the only meds I can take for it only work some of the time. So I spend a lot of time thinking about all kinds of things while waiting for sleep to find me! LOL
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post #17 of 23 Old 06-15-2018, 08:01 PM
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Quote:
Originally Posted by Chris Jacobs
Now go look at the fiat 500 system. The selections for the system is auto,sport,rain/snow. This clearly shows the software is tuned heavily towards AWD with the option for a rear wheel drive bias.
Its amazing the level of control they can exert over these systems just by tweaking the software, but, I don't think its possible to give this system rear wheel drive bias. The front propeller shafts are permanently mechanically connected, they can't be disconnected or have their engagement varied so its only possible to deliver up to a 50-Front-50-Rear split. You can get 60-Front-40-Rear but there is no way it can do 40-Front-60-Rear or anything like that.

Quote:
Originally Posted by Chris Jacobs
But if the issue is software based either way your looking at a ton of code to find why it is happening.
Meh, code doesn't scare me. That is my professional trade and academic background. I had started down the path of integrating a microcontroller into the primitive ABS system in my old suv (a 97 s10 blazer) to potentially take control of the abs pump and add some linelock solenoids to create my own brake-lock-differential setup, but it was too much hassle for too little reward, especially once we realized we could afford this new jeep!

This jeep by the way is my umpteenth vehicle (14th, maybe), don't worry I have had plenty of experience driving and working on many different vehicles over the years since my old man is an ASE certified master mechanic, all we ever do is tinker with things. This jeep is supposed to be one of the two vehicles in my current fleet of six that I don't crack open and work on but of course I'm still highly interested in how it works.

Anyways,

Quote:
Originally Posted by Chris Jacobs
If the shaft was balanced with dynamic tension in mind or is out of balance and dynamic tension is forcing it to act balanced then the shaft may vibrate at given speeds if it is spinning freely. Vibration then could be transferred by the center support bearing into the cabin where it starts making noise and may even be amplified by the cabin itself.
This seems plausible to me. I really do want to know the exact source and cause of the sound, for sure. I just don't want to jump to the conclusion that the buggy will have some premature failure because of it when we really don't know enough to be sure of that yet.

If I ever have enough free time I still want to slap the go-pro under there and see if I can catch whether or not the driveshaft is spinning while this noise is being produced. I'm almost certain it must be, but no way to prove it without sticking a camera down there and watching it.

We'll get to the bottom of this someday.
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post #18 of 23 Old 06-16-2018, 05:16 PM
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Originally Posted by arudlang View Post
Its amazing the level of control they can exert over these systems just by tweaking the software, but, I don't think its possible to give this system rear wheel drive bias. The front propeller shafts are permanently mechanically connected, they can't be disconnected or have their engagement varied so its only possible to deliver up to a 50-Front-50-Rear split. You can get 60-Front-40-Rear but there is no way it can do 40-Front-60-Rear or anything like that.
Yes it is amazing for sure! Jeep claims with this system 100% torque can be transferred to any one wheel. That means the system can bias either the front or rear axle by 100%. I think the animation in the link might be a little simplified. I think that along with the dog clutch in the front PTU there are wet clutch packs as well allowing power to be removed or cut to the front. This is the only way to get 100% power to one rear wheel.

Edit: In doing some reading on the fiat AWD as I had never looked much at them before it seems my assumption that sport mode became heavily RWD bias was off. Good thing I did not put fact in front of that one. LOL When we look at most AWD cars or even some FWD based 4x4 this is what they do to crank up the fun factor. Fiat it seems uses this mode not only for how it will get power to the ground but to boost engine,transmission and steering performance. So no this system as shown may be correct for the fiat and rear bias may not even be possible. This still leaves us with this system on a Jeep being able to put 100% torque to the rear axle. My guess is Jeep added some trickery around this system to allow that.


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Originally Posted by arudlang View Post
Meh, code doesn't scare me. That is my professional trade and academic background. I had started down the path of integrating a microcontroller into the primitive ABS system in my old suv (a 97 s10 blazer) to potentially take control of the abs pump and add some linelock solenoids to create my own brake-lock-differential setup, but it was too much hassle for too little reward, especially once we realized we could afford this new jeep!
I just saying it is a lot of code to go through and compare to find a problem that may only exist in some units. Then if it is hardware figuring out a software fix that does not affect the system performance will be tricky. For example looking at how the system is working at speeds above 40 mph that does not make this noise then applying that to speeds between 30-40 mph might solve the noise but make the ESC or fuel economy suffer. If it is an issue with the ESC changing it's programming might affect how well that system works within the 30-40 mph range. It is a heck of a mess.

Interesting though I googled this same issue with the Fiat 500x and nothing comes up. So I think the issue is some sort of conflict between Jeeps software and the hardware. Maybe Jeeps software to work this system in a 4wd mode is so aggressive it makes the hardware complain?

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This jeep by the way is my umpteenth vehicle (14th, maybe), don't worry I have had plenty of experience driving and working on many different vehicles over the years since my old man is an ASE certified master mechanic, all we ever do is tinker with things. This jeep is supposed to be one of the two vehicles in my current fleet of six that I don't crack open and work on but of course I'm still highly interested in how it works.
With that type of experience then you should know each have their own driving characteristics and feel. That means you too should be able to feel when your Compass is shifting power around. Yes moving power around 10% front to rear would take some serouse tuning in to detect. But 50% split your going to feel.


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Originally Posted by arudlang View Post
This seems plausible to me. I really do want to know the exact source and cause of the sound, for sure. I just don't want to jump to the conclusion that the buggy will have some premature failure because of it when we really don't know enough to be sure of that yet.
Wanting to know just to know is my main drive in wanting this to get figured out. But we do hope to have this Compass a long time as we really do love it despite some of its downfalls. So I do worry this could affect long term durability. We are hoping that if we are still loving this little Jeep in a year or two that we will buy Mopars lifetime warranty for it and the fact we can do this eases my mind a bit. I have seen post of this warranty replacing engines and transmissions in Jeeps that had mileage pushing 140k so it seems they are standing behind it strongly.

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If I ever have enough free time I still want to slap the go-pro under there and see if I can catch whether or not the driveshaft is spinning while this noise is being produced. I'm almost certain it must be, but no way to prove it without sticking a camera down there and watching it.

We'll get to the bottom of this someday.
I keep thinking nearly the same thing except we don't have a go-pro instead we have a lot of old cell phones that can shoot video laying around. Maybe I'll strap one under the Jeep then make up a system of blowing the horn or something to indicate speed or operation mode so I can relate these things to the video. If I lose a couple of these old crappy phones in the process I'm not going to be cracked up over it. LOL

Last edited by Chris Jacobs; 06-16-2018 at 07:50 PM.
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post #19 of 23 Old 06-16-2018, 09:37 PM
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Ok I figured out the 100% torque available to anyone wheel. It is technically correct but really a bit of wordplay and if you end up in a situation where you stall your front wheels don't expect the rear to be of any help. 100% torque (or maybe something near that) is only available to the rear if the front has lost all traction and is spinning. This is why when we see videos on this system climbing a steep hill with a turn at the top if there is not good full speed it gets jerky and is start stop on the front wheel spinning. It is trying to apply enough brake to send power to the rear without stalling the front axle.

They aren't switching the front off to move 100% torque to the rear they are just saying if the front wheels are free spinning active torque is not available to them but is to the rear if even one has grip. They are also careful to say 100% available torque as even free spinning wheels will eat a little bit of torque. So they can't say 100% of the engines torque is available to any one wheel I have to say this is pretty crafty wording. No wonder why they don't really want to get two deep into how their system works. LOL But really no matter how they are keeping these little Jeeps moving in adverse conditions or terrain they still have 2 of the most capable SUVs within their class for the price.
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post #20 of 23 Old 06-18-2018, 03:10 PM
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Quote:
Originally Posted by Chris Jacobs
We are hoping that if we are still loving this little Jeep in a year or two that we will buy Mopars lifetime warranty for it and the fact we can do this eases my mind a bit. I have seen post of this warranty replacing engines and transmissions in Jeeps that had mileage pushing 140k so it seems they are standing behind it strongly.
If you are going to get the big warranty then who the heck cares if this noise indicates a potential long-term issue? Just let warranty cover it.

Quote:
Originally Posted by Chris Jacobs
If I lose a couple of these old crappy phones in the process I'm not going to be cracked up over it.


Quote:
Originally Posted by Chris Jacobs
Ok I figured out the 100% torque available to anyone wheel. It is technically correct but really a bit of wordplay and if you end up in a situation where you stall your front wheels don't expect the rear to be of any help. 100% torque (or maybe something near that) is only available to the rear if the front has lost all traction and is spinning. This is why when we see videos on this system climbing a steep hill with a turn at the top if there is not good full speed it gets jerky and is start stop on the front wheel spinning. It is trying to apply enough brake to send power to the rear without stalling the front axle.

They aren't switching the front off to move 100% torque to the rear they are just saying if the front wheels are free spinning active torque is not available to them but is to the rear if even one has grip. They are also careful to say 100% available torque as even free spinning wheels will eat a little bit of torque. So they can't say 100% of the engines torque is available to any one wheel I have to say this is pretty crafty wording. No wonder why they don't really want to get two deep into how their system works. LOL But really no matter how they are keeping these little Jeeps moving in adverse conditions or terrain they still have 2 of the most capable SUVs within their class for the price.
Yeah I'm glad you did more homework on that because when I read the first sentence of the first post since I last got on here I immediately went and I thought I was going to be writing up another flaming post!

They are crafty with their wording, and you also have to watch out for marketing people on their team just plain screwing up. For instance way down on the https://www.jeep.com/2018/compass/capability.html page they have a paragraph about selec-terrain with an error in it:

Quote:
Dial in optimum performance. The Selec-Terrain® Traction Management System is standard on all Compass 4x4 vehicles. It allows the driver to choose from up to five on- and off-road modes so they can tackle a variety of surfaces. The settings coordinate 12 separate vehicle systems including: throttle control, accelerator pedal response, transmission shifting, transfer case operation, traction control and Electronic Stability Control
That is a page dedicated solely to the Compass and we all know there is no transfer case. Marketing people mis-type things all day long, so I wouldn't doubt there is some place somewhere that someone said "100% torque can be sent to the rear" but that would be inaccurate to say. (Notice that nowhere on that page I linked to do they make that claim, in fact I do not see anything on Jeep's website that claims the Compass can send 100% of the torque to the rear currently.)

Yes the word games are tricky indeed, but certainly no more than 50% power can be sent rearwards because the front wheels are permanently connected. No wet clutches or anything fun in the front besides the PTU. Whether or not the computer decides to brake the front wheels, those wheels are still receiving (their share of) the torque, which is torque that is then not going to the back, its being wasted on the front brakes.

They are able to get *some* power to all the wheels as needed and for non-serious-offroading intents and purposes thats all that matters. I would just suggest to anyone with a Compass who is struggling to climb that large hill with a turn at the top: you might have a better chance of success climbing it in reverse...
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post #21 of 23 Old 06-18-2018, 06:57 PM
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If you are going to get the big warranty then who the heck cares if this noise indicates a potential long-term issue? Just let warranty cover it.
Even if covered under a warranty having a vehicle you enjoy driving spend more time at shop than it does in your driveway is just a hassle. Not saying for certain this will be the case. Then the fact that to me this noise just bugs me and removes some of the enjoyment of it. But I'm starting to think mine may be louder than others. I can hear it with the radio halfway up and feel it in the small of my back in the seat. While I do often enjoy listening to the radio while driving there are times I'm out driving to escape a bunch of noise and have the radio off. This is when this issue drives me a bit batty. If this does turn into a well known failure down the road vehicle value will be effected. Then I think about those that for whatever reason do not extend the warranty.


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Originally Posted by arudlang View Post
Yeah I'm glad you did more homework on that because when I read the first sentence of the first post since I last got on here I immediately went and I thought I was going to be writing up another flaming post!

They are crafty with their wording, and you also have to watch out for marketing people on their team just plain screwing up. For instance way down on the

That is a page dedicated solely to the Compass and we all know there is no transfer case. Marketing people mis-type things all day long, so I wouldn't doubt there is some place somewhere that someone said "100% torque can be sent to the rear" but that would be inaccurate to say. (Notice that nowhere on that page I linked to do they make that claim, in fact I do not see anything on Jeep's website that claims the Compass can send 100% of the torque to the rear currently.)

Yes the word games are tricky indeed, but certainly no more than 50% power can be sent rearwards because the front wheels are permanently connected. No wet clutches or anything fun in the front besides the PTU. Whether or not the computer decides to brake the front wheels, those wheels are still receiving (their share of) the torque, which is torque that is then not going to the back, its being wasted on the front brakes.

They are able to get *some* power to all the wheels as needed and for non-serious-offroading intents and purposes thats all that matters. I would just suggest to anyone with a Compass who is struggling to climb that large hill with a turn at the top: you might have a better chance of success climbing it in reverse...
Yes the wording is not what it should be. Torque is such a tricky thing. But truth is this system can result in nearly 100% torque being sent to ground by any one wheel but only under certain situations. And this is where the claim "available torque to any one wheel" should be followed by an asterisk. You really almost need to draw a simple diagram of the driveline and turn it into a torque flow cart. then think of it like an electrical circuit with the tires being earth ground. Remember a driveline is not like an engine it does not build torque through RPM it simply moves it around through rotational force.

In 2WD open diff torque is 50/50 if both wheels have traction but when they slip either of the wheels can receive 100% of the torque present in the driveline with normal driveline losses accounted for. I'm not going to go into locked diffs here as it does not matter. What does matter is torque to ground. In the case here without intervention the wheel without any traction ends up with 100% the torque but no way to but that torque to ground. If we flowchart this like and electrical circuit it is a short that is not doing any work. Now if we add brakes to that wheel we can force 100% available torque to transfer to the other wheel that has traction. This is a no brainer most everyone gets this.

Where things get interesting is with the system in our little Jeeps Yes it can put nearly 100% of the available torque to ground even by rear one wheel. But like most consumer 4WD systems there are catches. In order to do this the right front wheel has to be free spinning and the left front wheel stalled by terrain or brake lock. If that right front is spinning it is receiving torque but not using any torque so that torque will flow down the drive shaft to the rear axle where the rear diff can send it to either wheel if needed by the the brake lock.

The problems come from when torque is transferred to the left front and right front is stalled or the whole front is stalled nothing goes to the back. True the front is putting 100% torque to the front axle but then it can't suddenly choose to put torque to just one rear. !00% torque only means something if that torque produces work. But In a system that Jeep is making it seem like these have if the front were stalled the front could be cut loose from the drive line and 100% torque then sent to the rear to push or pull the front out. Giving these Jeeps the ability to disconnect the right front wheel from the diveline after the PTU/PTO is all that they would have needed to add to this same system to do this. Which is what I thought they had done till really looking at it and realizing the word play. It is not dishonest just not what comes to mind

But even conventional 4WD systems have similar limits if not set up for perfect off-roading. In a 4wd rear drive platform If you wedge both the rear wheels your just as stuck as you would be in the Compass with its front wheels wedged. With the 4wd locking the front and rear axles together torque gets sent to both axles still but the axles cannot rotate separately if the front tires can't rotate they can't pull you out. But if the front gets wedged you can shift into 2WD and hope the rears can push or pull you out. If you have the perfect 4wd system it can be operated to go into 2WD mode choosing either FWD or RWD.

The fact that these little Jeeps lead with their main drive axles is what gets them in trouble. So it is more important to take on situations where a wheel can become wedged diagonally which is the preferred way anyhow. Just for me I think if possible I would let the left front lead because if it get stucks torque will flow towards the front PTU and right wheel. If the right front starts to spin torque will start flowing more to the rear axle up to that 100% still available to the driveline. Where if you drop the front right first and wedge it all your going to have to help keep you moving is the right front.

If going up a steep hill again your ok going forwards but if the turn up top ends up stalling the right front going is about to get rough. But if it lifts the left front and the brake lock kicks in it is going to be easy. If both fronts can spin your good. But you can always hunt for traction turning the wheel to try to get that right front spinning. Well as long as there is not a cliff,tree or rock right these that make you have to turn hard at the top anyway.

Still these are pretty darn much the most capable in class for sure and I we still love our little orange beast! Went wheeling a bit last light and had a blast and about to make a post on it as well as a little discovery post hope you join in.
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post #22 of 23 Old 06-18-2018, 10:00 PM
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Now if we add brakes to that wheel we can force 100% available torque to transfer to the other wheel that has traction. This is a no brainer most everyone gets this.
Quote:
Originally Posted by Chris Jacobs
Where things get interesting is with the system in our little Jeeps Yes it can put nearly 100% of the available torque to ground even by rear one wheel. But like most consumer 4WD systems there are catches.
"Available torque" is a nasty, tricky term because it matters 'where' in the driveline you are referring to/measuring. Just remember you can only get half of the input torque to either wheel in an open diff. If 1000 ft lbs is the input to the differential and that is the number you consider to be the "available" torque, each wheel will get 500 lbs of that force each and never any more. You cannot send the full 1000 lbs to one side, or even 501 lbs, and though it makes us sad it is what it is (damn physics).

Full honest disclosure, what follows may come off as a much more confident understanding than I actually have on how this all works and I'm not always right but based on what I understand, this is how I understand it :P

Open differentials have a TBR (Torque Bias Ratio) of 1:1, always. Or as I like to think of it, 50/50 split. They cannot bias torque from one side to the other. The torque that can be applied to one side is the max of what can be applied at the other side (think tractive force, except I'm not going to get into how weight over each tire factors in to keep it much simpler). So without magic brake voodoo, consider a FWD open diff car with the classic one-tire-on-pavement, one-tire-on-ice scenario. If only 200 pounds can be applied to the ice side before it slips, then only 200 pounds can be applied to the dry pavement side as well, 400 total and maybe not enough to overcome inertia and you don't move. Add in brake voodoo, you can apply 300 pounds of resistance to the ice side via the brake, add that to the 200 the ground can take, now you have the total force at the ice side up to 500 which means you can also now put 500 down on the pavement side too and your total force (500 + 200) makes 700 at the ground through both wheels and perhaps now you have enough to roll away. Thats how brake-diffs get you rolling, not by putting 100% of the input torque to any wheel but by getting up to 50% of the input to the high traction side. Its way better than nothing but its no contest compared to limited slip or locking systems, which is a big part of why I don't consider it to be a true 4x4 as much as just a really good AWD.

So now I've been talking about one differential, the front. We/the computer have the option to hook up the second (rear) open differential, direct lock at the PTU and for simplicity's sake assume the wet clutch fully locked up as well, where does that leave our power distribution, you may ask. Well, I am wondering the same thing because it depends on how the PTU is hooked up to the output of the transmission. If it is direct (and I think it must be), then theoretically all the input power could be sent to the rear but only in the condition that neither of the front wheels have any traction whatsoever. Whatever is going to the rear is going to be the input less the amount that can be taken&applied in the front. Then the rear has to split that amount 50/50 according to the rules of an open diff and the brake voodoo.

So in the event that the front two wheels are resting on ice, and the rear wheels are on bare pavement, almost all the input power can go to the rear axle but only up to half of that can go to either side there. So if its three tires on ice, a little less than half of the input can make it to the one good tire, front or back. As long as the brake voodoo works as intended each low-traction tire can put down whatever it can up to the point of slippage and between all four of them this is almost always going to be enough to move you forward, up to the point where there is more inertia to overcome than the engine can (or computer will) provide (ie, stopped facing straight up a super steep hill).

This is all my brain can put out for the moment, I should take some time to error check it but I'm sure Chris will handle that for me so I'm not too worried =D I have the same conclusion, these things are still the most capable in their class and more than enough for most things that would be thrown at them.
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post #23 of 23 Old 06-19-2018, 03:07 AM
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"Available torque" is a nasty, tricky term because it matters 'where' in the driveline you are referring to/measuring. Just remember you can only get half of the input torque to either wheel in an open diff. If 1000 ft lbs is the input to the differential and that is the number you consider to be the "available" torque, each wheel will get 500 lbs of that force each and never any more. You cannot send the full 1000 lbs to one side, or even 501 lbs, and though it makes us sad it is what it is (damn physics).

Full honest disclosure, what follows may come off as a much more confident understanding than I actually have on how this all works and I'm not always right but based on what I understand, this is how I understand it :P

Open differentials have a TBR (Torque Bias Ratio) of 1:1, always. Or as I like to think of it, 50/50 split. They cannot bias torque from one side to the other. The torque that can be applied to one side is the max of what can be applied at the other side (think tractive force, except I'm not going to get into how weight over each tire factors in to keep it much simpler). So without magic brake voodoo, consider a FWD open diff car with the classic one-tire-on-pavement, one-tire-on-ice scenario. If only 200 pounds can be applied to the ice side before it slips, then only 200 pounds can be applied to the dry pavement side as well, 400 total and maybe not enough to overcome inertia and you don't move. Add in brake voodoo, you can apply 300 pounds of resistance to the ice side via the brake, add that to the 200 the ground can take, now you have the total force at the ice side up to 500 which means you can also now put 500 down on the pavement side too and your total force (500 + 200) makes 700 at the ground through both wheels and perhaps now you have enough to roll away. Thats how brake-diffs get you rolling, not by putting 100% of the input torque to any wheel but by getting up to 50% of the input to the high traction side. Its way better than nothing but its no contest compared to limited slip or locking systems, which is a big part of why I don't consider it to be a true 4x4 as much as just a really good AWD.

So now I've been talking about one differential, the front. We/the computer have the option to hook up the second (rear) open differential, direct lock at the PTU and for simplicity's sake assume the wet clutch fully locked up as well, where does that leave our power distribution, you may ask. Well, I am wondering the same thing because it depends on how the PTU is hooked up to the output of the transmission. If it is direct (and I think it must be), then theoretically all the input power could be sent to the rear but only in the condition that neither of the front wheels have any traction whatsoever. Whatever is going to the rear is going to be the input less the amount that can be taken&applied in the front. Then the rear has to split that amount 50/50 according to the rules of an open diff and the brake voodoo.

So in the event that the front two wheels are resting on ice, and the rear wheels are on bare pavement, almost all the input power can go to the rear axle but only up to half of that can go to either side there. So if its three tires on ice, a little less than half of the input can make it to the one good tire, front or back. As long as the brake voodoo works as intended each low-traction tire can put down whatever it can up to the point of slippage and between all four of them this is almost always going to be enough to move you forward, up to the point where there is more inertia to overcome than the engine can (or computer will) provide (ie, stopped facing straight up a super steep hill).

This is all my brain can put out for the moment, I should take some time to error check it but I'm sure Chris will handle that for me so I'm not too worried =D I have the same conclusion, these things are still the most capable in their class and more than enough for most things that would be thrown at them.

I'll leave you with this to think about. We agree that if 100% torque is available and both wheels of an open diff have 100% traction capability each wheel gets 50% of that torque and not only will they receive that torque they have to use that torque somehow. The moment either wheel has a reduction of traction the available traction to whole axle drops. Then what is left over is again split 2 ways. This is the physics of the open differential. Now add BLD and you add some more physics. Instead of relying on traction to spit torque we use friction from the brakes which mostly means torque is allowed to build back to 100% available to the axle.

As long as the goal is to allow the differential to work as intended the the 100% available torque is still split 50/50 by the wheels one wheel eats it share of torque by putting it into motion needed to create or maintain momentum the other wheel is eating up to it's 50% by friction turned into heat by the brake on that wheel.

But what happens if we force the open differential into another key role that no longer allows it to split power in short we break or brake it or better break it using the brakes?

What happens in an open diff when one wheel has enough traction to use 100% of power available to the axle and we lock the opposite wheel so it cannot rotate at all? The wheel that is locked can no longer transfer torque to ground and it can't dissipate that torque in any way. Remember if the axle has enough traction it will get 100% of what is available to it and must use it.

Now visualize how the open diff works anytime wheel speed needs to change from side to side but power needs to be able to move around. The spider gears start working and the carrier speed changes. If we lock up one axle the carrier spins around that axle transfering power to the other wheel. Have we not just turned a differential into a clumsy bit wasteful way to send all power to just one wheel?
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