ok when i drive over 55 i have a shakking through the car after driving for a while if you put it in reverse it feels like it is binding up and when you put it in park you can hear a thumping sound comming from the drive train i have repaced both cv shafts in the front (they were bad) and the passnger side hub i am going to replace the ball joints with after market ones because it pulls to the right and the stock ones do not have a camfer adjustment is the binding a diferential problem or a transfercase problem also if while the engine is off if you shift to nutral you can feel it release the tension on the drive train.
Jeep has used a few different transfer cases on different years and some require a special fluid, make sure it has that fluid in it. Some of the transfer cases work similar to a limited slip differential and determine when you need the front wheels engaged, with the wrong fluid they can cause problems. Also the front driveshaft on some of the Jeep Grand Cherokee and Grand Wagoneer models had a CV joint instead of a standard U-joint normally found. They are kind of notorius for giving a hard to locate vibration. NAPA sells a replacement driveshaft with a standard u-joint instead of the CV joint. Good luck.
Grab the front drive shaft at the rear u-joint yoke and try to move it side to side and up and down. If it wobbles the transfer case output bearing is shot.