When I pull my 98 XJ into gear there is a loud bang. I googled and googled - which lead me to change out the u joints. That didn't help. It is significantly worse if I am on a hill, or if I quickly put it into gear and don't stop at neutral. Any ideas what is causing this?

 

Checked the condition of your motor and tranny mounts yet?

 

Tranny mount is good - checked that just a little bit ago. The motor doesn't seem to be moving anymore than normal so I haven't checked the motor mount. Think that's the issue?

 

Very likely.

Time for some noggin pokin on your end.

 

Ok, so I found the issue. There is just some slop in the rear differential. When I pulled the drive shaft out, I grabbed a hold of where the ujoint seats - then the part where the ujoint seats runs into the rear diff. It moved about half an inch either direction and there was an audible bang just from me twisting it. Is there anything I can do other than rebuilding the entire rear diff? I just put brand new fluid in it (85-140).

 

Good job!!

Used rear end from a junkyard?

 

Crap, I think this is my problem too ha ha.

Are these gears going to chew themselves apart or are they already dead/dying? Can I drive for years on it like every other XJ problem?

 

It will fail sooner or later.