I burned up my 4x4. 2 wheel stil works fine. I'm wondering what years of comanche transfer cases will fit with the 90 cherokee or how hard it is to replace the busted 4 wheel drive [addsig]
If you just have part-time 4WD it should be the NP231
I don't think they offered full-time that year but please correct me if I'm wrong and ignore the rest of this post
not sure what years or even if it was used in a Comanche.
as far as fixing it, it depends on what broke, there are only about a dozen parts inside the whole t-case so depending on what broke it should be fairly simple, if 2wd still works, and you can shift out of it, the main shaft probably still works as does the shift fork and the rail. After that all that is left is the chain, the front output shaft, and the planetary gears in the main shaft, each of the 3 possible broken parts is easy to replace. If it is the shift rail or fork that's broken it's even easier
edit: here is an SYE writeup I did, it has some pictures to show you the inside of the NP231 to show what it looks like.