Okay so im completely new to this jeep stuff but im very interested in learning more about them, but my u -joint thats connected to my drive line keeps braking i have been threw 2 i broke the first one wheeling then i bought the new one and placed it on there and boom 5 miles down the road it snapps off and i look and the caps that connect to the umm other part not sure of what it is but not the ones that connect to the drive line are snapped off.

so some info on the jeep is its a 1988 cherokee 4.0 and its lifted on 2in blocks i noticed as i pull away the rear axel shifts forward a little bit and im not sure if this is supose to happen or if maybe thats the problem ..... Any suggestions on why they keep braking ?

 

That movement in the rear is called Axle Wrap and is probably caused by those lift blocks. I'd say it's safe to assume that's what's causing the U-Joint carnage.

The best way to fix it would be to remove the blocks. Shackles are a much better route.