So this has been happeneing to my current lifted 2000 Grand Cherokee (109k miles) and also happened on my old 99 stock Grand Cherokee (so I figured it was a common issue) but I can't see to find much on this topic. So basically only on cold backups (i.e not driving any distance before backing up) my jeep pops/clunks from the rear. Now at first I thought it could be a tranny problem but not only is the noise coming from the back, but when I shift it into nutral (while still rolling back) the noise persists. The slower I roll the less popping it makes, seems to pop more when turned and in reverse. Then after any short amount of foward driving, I can back up with no noise. Could it be the diff gears? Or something in the suspension? I don't know all that much about suspension issues so I need help. Let me know what you think thanks!

 

The slip yoke needs lubing or you got a bad u joint in the driveshaft.If it was the gears or suspension it would do it always not just here and there