NP231 chain bad? clunk and clank

After scowering the posts I think I have figured out what sounds like metal breaking and clanking on the 87 XJ. When looking at the front drive line (4wd, driving forward, and turning) it looks like it binds for a second and makes a bad cracking noise that makes the whole front end jump and then it catches again. (some have suggest axle u-joints)

Is this a clear indication that the T-case needs to be rebuilt b/c the chain is gone on it and it is just catching here and there? when forward no problem, only does it when turning.

axle u-joints

well it looks like the axle u-joints have it. three replies between here and another and everyone says U-joints. thanks much!

My 231 transfer went to skipping at 100,000 and it sounded like machinegun fire anytime I got on it fairly hard in 4 low. A new chain was the trick.