Model 20 open diff 2 peice axles, weekend project. What could be the cause of slop in the rear end where it sort of clunks when you go from backing up in reverse to going forward in drive? I am sure there could be several things. I was going to check the 2 peice axles to see if one is bad, check the ubolts, the driveshaft and ujoints are ok. If I eliminate these external things, what internally should I look for? Seems like I would have more of a problem if it were spiders or the ring & pinion but I wasn't positive of that.

If you're still running the 2 piece POSs then you probably have one that is now really 2 piece. Common problem.:D

Is it on the jeep in your sig? With the detroit rear? If so then Yeah........probably time for an axle change. They are......"the weakest link". ;)

If everything looks good then pull the cover and take a look. It is probably time to change the oil anyway

It is actually a buddy's jeep that I am trying to help him with. I have the one peice in mine. Anyhow, I am expecting the axles but there seems to be a few other potential problems. Thanks for the responses.

Rebel.....I just realized your sig is basically my jeep as well.

With exception that mines an '81 i'm running the 258 that came stock. T-18 , Dana 300, M20-Detroit-Mosers-4.10's, D30 Powerlok. 35" MTR's. 2" Rancho SOA.