My Jeep Compass Forum banner
1 - 1 of 8 Posts

· Registered
2 Posts
I don't know how loud you mean. Past a certain volume any loud sound is not normal, but in general some humming from the AWD system doing its work is normal.

It tends to happen when you have been cruising at highway speed and the vehicle went into front wheel drive (FWD/2WD) to save gas, then when you decelerate from cruising highway speed the vehicle preps itself to re-engage AWD if needed. This means it engages the variable clutch in the rear differential to bring the ring gear and the propshaft up to speed but it has not yet engaged the front dog clutch in the power take-off unit (PTU). The rear diff and propshaft need to be spinning as close as possible to the same speed as the front diff in order for the dog clutch to engage smoothly, a dog clutch is a toothed gear that is only engaged or not engaged, its not variable like the RDM (rear differential module) clutch. If the two spinning assemblies are not closely matched in speed it can make a hard CLUNK for that dog clutch to engage, hence the use of the rear clutch to wind the back half of the AWD driveline up to speed in that situation so the car can immediately engage AWD if conditions suddenly demand it. Most of the time it turns out that AWD is still not needed as you decelerate, the car can remain in 2WD but its still 100% ready to pop that front clutch in if suddenly needed. In this state of 2WD with AWD prep is when the humming occurs, either because the rear variable clutch is not 100% engaged or just the sound the propshaft makes when its spinning but not engaged at both ends.

In any case, its normal. Its designed. These part-time AWD systems are not silent. Its generally inaudible unless your radio volume is down way low. Its just part of how the system works. It is not as quiet and smooth as the marketing teams would lead people to believe, but it does work well.

Now if its so loud that it can be plainly heard over the radio at moderate volume, or it suddenly starts doing it louder than before, there could be an issue with a bearing or lubrication, etc. Exactly what that threshold is between normal volume and loud enough to need it looked at is kinda hard to describe. Kind of a judgement call. I heard mine doing it plainly from day one, but I soon determined its just part of AWD operation and have driven 55k miles ever since still hearing it constantly but no issues.

There was a software update after many complaints that altered the algorithm of when and how the car does its AWD prep, it used to do it at a lower speed that was much more noticeable, then they moved the range up to a higher speed where highway and tire tread noise tends to cover it up more (but its not gone). 1 2019 should have came from the factory with that update and surely your dealer has already found that and done it, but might be worth checking, there is a TSB number from old discussions on this forum here if you use the search (this topic has been talked about many, many, many times, you would have found more than you could read if you tried the search).
My 2016 automatic compass hums as if the rpm’s are where they should be at shift time but it doesn’t shift. You can speed up and the rpm’s may rise and fall back but the hum is there at any speed. Is this normal? Especially if all the windows are up it sounds louder.
1 - 1 of 8 Posts