Like a transmission mount ... 3 years ago, I started to have driveline vibrations, front and rear, on the Cherokee. After some troubleshooting, I determined the front differential suffered pinion bearing failure (pretty common for that differential). I bought a new axle and swapped it in. Helped a bit, but still had some front and back. Then I rebuilt the driveshaft myself and the front was no problem! Had some issues with the rear driveline vibrations. Always seemed to get worse after driving a bit. I did the "typical" Jeep things to get rid of rear driveline vibrations. Did a transfer case drop. Nothing. Then bought SYE kit and a few other goodies and had the transfer case rebuilt. Still had the problem. I figured it was the junkyard shaft that I rebuilt myself. While I have had good luck rebuilding cardan joints in the past, I thought that, maybe, I messed this one up. Brought it to Fleetpride, paid $130 for a rebuilt driveshaft with balance and .... Still bad. I was getting ready to scrap the Jeep by this point. I had been chasing these issues for three years. I missed out on a LOT of off roading trips because I couldn't drive the thing. I figured the differential was bad. I dumped 85w140 gear oil in it to see if that would quiet it down. Surprisingly enough, it did help. Great! So I bought another axle. By then, it started to get winter out and I wasn't really able to swap it. Over the winter, I noticed i started to get a real bad clunking. I figured it was a damaged control arm. A friend noticed it sounded like the transmission was hitting the floor. Sure enough, the transmission was hitting the floor. Started wondering if it was a bad transmission mount that was transmitting driveline vibrations into the cabin? Having had a transmission mount go bad before, it's usually engine speed related issues. Then I had someone brake torque it when I was looking underneath. Couldn't believe it! The transmission mount delaminated; when on the gas, the drivetrain would rock around and throw the driveline angles so far off that it would vibrate horribly. It didn't look terrible with weight on it. Ordered the $30 part from Rock auto. Played around with some stubborn bolts and ... IT FIXED THE ISSUE. 3 years. Over $1K later. And it was a $30 transmission mount. I've managed to put 250 miles on it in one week now. I have to make up for 3 years of not being able to drive it and putting more-than-necessary miles on the car.