I've got a 92 xj 4.0 auto with a 2.5-3" lift and 31's. when I let off the gas downhill my whole rear end kinda drones and vibrates and when I through it into reverse from drive, it makes a loud clank noise. Are these 2 different problems? Or is it a bed rear driveshaft u-joint? Or possibly a bad pinion bearing? Or is it that my drive shaft is sitting too far back on my slip yoke? Help please

 

Could be a few things. Get under there and check stuff out.

Could be ujoints, could be bearings in the axle.

The clunk could be a trans mount.

 

Ok that vibration I'm not too sure of though. The clunk might be a tranny mount but the vibes only happen under deceleration, with you foot on the pedal, even a little but, it doesn't vibrate but as soon as your foot leave the pedal I'd just vibrates like crazy. But I'll get under there tonight and check it out and get back to you.

 

Check your yoke angles, and your driveshaft u-joints, they could be very mildly vibrating. grease your slip yoke to fix that clunk, tranny mount is a good bet as well.

 

Things move differently under accel and decel....could be a few things.

 

Well I replaced the u-joint on the slip yoke side and that helped a lot but I still had a slight vibe when decelerating. So I looked at it again and someone didn't center the pinion side u-joint. So I took it apart (turns out its a brand new u joint) and I saw that someone had dropped a needle bearing in the cap soo the joint couldn't properly seat into the yoke. Took off the cap got a q-tip and positioned the needle bearing back in proper line and put the joint back on and now it's all centered and the entire jeep drives like a dream. Thanks for all the help guys!