So yesterday i got a wild hair and replaced a bad ujoint in my driveshaft at the axle, its been bad as long as I can remember. After doing so I took it out and although the clunk is less prominent it's still there. I can twist the rear driveshaft and there is no play in either ujoints. It doesn't clunk on take off (possibly because I've trained myself to avoid that from years of driving with the bad ujoint) but it does if I'm up at speed and release the gas and/or hit the gas again. Could this be a diff problem or a transfer case problem?

Here's a pic of the joint and its looks the same on the opposite end.

 

And a pic of the caps

 

Oh an it's a 90 4.0 4wd and has an NP242, no suspension mods.

 

Clunk

 

Years of driving with a bad u joint?

 

I'll be a bit more specific, my first car had a bad ujoint in it. The car got me from point A to B for 3 or 4 years I believe that joint was bad the whole time I owned the car and I drove it about 120 miles to get to town and back home.
The jeep has been bad for 3 or 4 years also, however, for the last 2 it has barley been driven 6000 miles because my work provides me with a vehicle.

 

Replace the other one.

 

I do like replacing ujoints for some reason so I'll do it but I don't think that's the problem. It's the whole driveshaft that moves it rotates at the axle and the transfer case not at either of the joints.

 

Still get a clunk when letting off gas and when pressing on gas after coasting. Any ideas?

Rear driveshaft rotates by hand at transfer case and at rear axle. Not much but easily noticeable.

 

You replaced both? I'd also check your u bolts to make sure they're tight and the axle isn't knocking, also grease your slip yoke splines. You can find out how with a simple google. Takes 2 minutes.

 

The driveshaft only had u bolts on the axle side and they are nice and snug, I'll grease up the slip joint tomorrow if I can while there is still light out.

 

Really need to replace the other u-joint on driveshaft..

 

U bolts that connect your leaf springs to your axle is what I meant. Most likely its the other u joint though.

 

Greased up the slip yoke finally. It was a lot stiffer putting it back into the transfer case which I assume is good. Forgot to check the u bolts around the axle but will when I can, but greasing the slip yoke seemed to do the trick. While under the jeep I rechecked the ujoints and decided to just finish replacing them all. I think I mentioned earlier that the driver side hub was going bad and I had already replaced the passenger side hub, but upon this inspection I noticed the front driveshaft was a little loose at the axle so after I replace those two I'm left with the double carden, so why not just finish it all right?