Hey guys, just bought a 98' xj with the ax15, np231, and chrysler 8.25. When shifting from any gear to another, once you release the clutch you hear and feel a clunk. If you shift real smooth, let the clutch out slow and have your foot off the gas you can get away without the clunk/thump. Im going to see if the parts store has 75-90 gl3 or gl4 tomorrow. Also, Il pick up 80-90 gear oil for the rear differential. The u-joints appear to be fine, I just replaced the rear shocks however the leaf springs are flat (bad??). Also, the jeep leans on the driver side and Im thinking the leafs are bad. The leaf shackle mount is rusty so Il order new ones. Any ideas guys, could it just need new fluid or are the worn leaf springs shoving the drive shaft into the rear end? Thanks

 

U joints to the naked eye can look fine but what your describing is 90% of the time u joint... Grab the shafts and pushe up and down or left and right... Dont turn cause of course they will have play turning... If they move at all when pushed and pulled then u got bad joints... Also make sure its in level ground and in N...

XJ rear leafs sag all the time... Gazillion threads about it already and u should be able to find the info u need...

 

+1 u joints. If the clunking is still there (mine does it to) then your rear suspension and the engine/transmission mounts are suspect

 

I gave the u-joints a good push and pull, there wasnt any play. I see they are greasable, il grease them up tomorrow. I know I need to replace the rear sway bar shackles, they seem rusty and cracked. The thump is getting worse, it isnt just when I shift. If Im coasting and then hit the gas, Im getting a thump that seems to be coming from the rear or the vehicle. Just replaced the shocks today, leaf spring bushings arent to bad either. Still think its a bad u-joint? If so il pick a new one up. Going to change the ax15 fluid with penzzoil synchromesh, says on the bottle its compatible with yellow metals.

 

i still think its a u joint... lol... check your motor mounts also... dana 35 or 8.25?

 

I checked the driver and passenger side motor mount, the rubber does not look bad (torn/ripped). It has the chrysler 8.25 rear end.

 

I'm having the exact same problem with mine. Just bought it a little bit ago an did the IRO hack and tap. Ax15 but with a Dana 35. I also have the flat and worn out rear suspension. Haven't looked into it too much but I doubt it's my I joints being that they are both brand new.

 

Check the tranny mount? How much slops in the rear end? Could be a loose pinon but unlikely, and I would just take that rear swaybar off and trash it you don't need it.

 

I didnt get a chance to change the trans fluid tonight, Im going to put it on a lift tomorrow and change it then. While on a lift Il have my friend help determine if the motor mounts, trans mount, or u-joints are bad. The u-joints have no play but Id bet money they are original, just like the rear shocks were. I really, really hope the rear end is not messed up. Il have to do a drain and fill next.

 

I doubt the rear end is jacked up...

 

Thank you, this helps calm my nerves. Im going to pick up new u-joints for the rear driveshaft. If I unbolt the rear of the driveshaft from the yoke on the diff, and slide the ds out, will the t-case fluid run out?

 

Negatory - the drive shaft yoke actually slides around on a long splined shaft sticking out of the transfer case (legendary slip yoke...). This is sealed from the transfer case and from the rest of the world by a rubber boot. Good time to pack that puppy with grease

 

Good idea salad, Il pick up some grease. I read people have clunking from there being a lack of grease in there. Regular wheel bearing grease ok?

 

Yep that stuff will work fine

 

Clunk is about 95% better. Didnt have time to order the spicer u-joints so I went to the parts store and bought the red cap brute force u-joints with a lifetime warrant. Also drained the nasty trans fluid and filled it up with penzzoil synchromesh. When I pulled the rear drive shaft off the shaft of the t-case I lubed it up really well with grease. Shifts way better and the clunk is almost completely gone. Going down now to pop the cover off the rear pumpkin and change out the fluid with 80-90 gear oil.