I am looking for options on updating my tcase to a stronger one. Can I use either a tcase off a newer XJ or one out of a Ram 2500? As long as its a np231 or np231j or even a np231hd its still the same tcase with better parts isnt it?

 

Nope, there are some external differences across the NP231 line. Are you breaking a lot of transfer cases? They're pretty stout. I'd stick with the NP231J and do the regular upgrades and protect it properly

 

Just wanna upgrade it to handle 38s so Im not breaking them all the time and I dont like the way my transfer case self lubes its self

 

There are plenty of guys running 40"s and not breaking 231's if you manage to break one, you're driving wrong lol Just do the hd upgrade, search and look for the info on bigger chain and sprockets

 

231 is fine for that...

What's wrong with the oil pump?

 

First thing is, yours is 21 spline and all the others you're thinking of are 23 spline.

 

Cant I convert to 23 spline by swapping the tcase or am I just stuck with what I have.

 

I don't know. The splines are 21 between the trans and t-case. Something would have to be done.

 

Could I swap in a newer trans or would that not work with the renix set up

 

NP input gears are the same across a wide variety of transfer cases. If you were to swap you just carry the gear over.

Still don't see why you want to get rid of the 231 though...