my cousin has a wj and we just replaced all of the u joints because his front one was shot, we replaced them all and the front one is still clicking, what the hell could be the problem? all the other ones are fine

 

I am bumping this because I have the same problem. I have replaced both axle joints and both hubs and wheel bearings were replaced because they were shot and it is still making the clicking noise. I have also checked the fluid level in the diff and it is full.

 

It's probly the transfer case. Grand cherokees are known to have that infamous clicking noise from the crappy np249 transfer case.

 

possible axle joints...