I think my t-case is on its last leg. When i slow down on the highway and sometimes in town it makes a clicking sound. It sounds like the chain is skipping off the bottom of the case. I have heard that the NP231 is somewhat notorious for the chain stretching, sounds like that could be my problem. I am just guessing about the t-case chain, it is hard to pinpoint the noise but it sounds like the t-case. Is my diagnosis reasonable? Any other thoughts? Also assuming the t-case is bad should I try to rebuild it or just replace it. Any leads on a cheap NP231 replacement would also be appreciated. Any info/opinions are welcomed. Thanks.

If the chain is stretched enough to be hitting the bottom of the tcase, then there will be metal shavings in the oil....

Drain the oil and see what you get. The chain is fairly easy to replace.

I would be really supprised to find out that a 99 tj had a streached chain. Last one I fixed was a beat to death 88. It was the first time the case was opened. Not saying it couldn't be, but I expect that it is not the chain. Go through and check all the fluids, Heck replace it if it is time and look for shavings as suggested and discolored oil. While changing the chain is not difficult it requires a few special tools and While I could do it in about 3 hours (I like to do it on a bench) I wouldn't want to do it unless absolutely necessary.

Berings going out tend to tick as described. I would make sure what was wrong before I threw parts at it.

Jeff