I, like many, have the CLUNK around 38 MPH. It is the AWD kicking in when the temps are around 40 or below. Do me a favor, go drive the routes you normally do and where you hear the noise. Then, LOCK the AWD and do it again. The clunk should go away. I've just come to expect it. Lets me know its working
. As for a grinding noise, I have no such thing. No signs of leaking anywhere under the Jeep either, as I just did an oil change and full inspection last weekend. My Trailhawk Cherokee always had something leaking by this point (9,000 miles).