Unless you put some ladder bars on the diff, it is the springs twisting and the tires walking forward. It could also be bad ujoints. Unless you put a double u-joint cv joint on the driveshaft, it is going to eat u-joints, especially when applying pressure to the system. It could also be the bushing in the tail shaft of the transmission wearing out, causing the driveshaft to wobble....does it leak trans fluid when driving? That s why...............So you are probably thinking if i just wanted to drive it every day, i probably should have left it stock. Having the driveshaft at more than 4 degrees causes a lot of problems. It can destroy transmission, eat u-joints like candy and possible even brake a leaf spring.............But if you have to.....double u-joint cv joint drive shaft just like the one on the front diff. Dodge saw it was a problem and fixed the front.......ladder bars on the rear end will keep the springs from twisting. After you get that far, pull the tail shaft off the transmission and have a trans shop press i a new bushing and seal......do all of that and you will get a couple of years out of it without a problem. But you will eventually have another problem........My bro has a transmission shop. I saw a lifted ram get towed in that the entire tail shaf was ripped off the unit because of the lift kit.............he fixed it and told the customer there is no warentee because it will happen again. Lifted with big tires puts a lot of strain on the drive system. rule of thumb, 35 inch tires needs 4.10 gears. 37 inch 4.56. That is how toy keep the strain off the rest of the drivetrain but is still going to cause problems with the rear diff bearings and wear and tear on the ring and pinion.