LKN_xj

My jeep is a 1991 XJ Limited with a 4.0 and automatic transmission. It currently has the select track NP242J T-case. And it's tired...350k miles kind of tired. The t-case chain is slapping and I can hear a bearing grinding. It needs to be rebuilt at a minimum. Everything seems to work fine but it's loud and pending failure. The T-case has never been cracked open...

The route I chose was to purchase a junk yard NP242, and swap it in to keep me going while I do a SYE and rebuild my current 242. I found a junk yard 2 hours away advertising a NP242. This past weekend I went and got it. Good news is that it was there...bad news is that they need their eyes checked and it's actually a NP231. The input shaft is .6" long and it's a 23 spline.

So the question is......

Can I know for certain the transfer case input shaft length and number of splines of MY NP242 without having to pull my transfer case off. Since I'm now stuck with a 231 spare, and it's rare I need to drive in winter weather (live in NC), I imagine the 231 would suit my needs and the SYE options are greater. I just need to know that when I take my 242 off, this 231 will have a compatible input shaft.

The things I know are:

- In 1991 spline count went from 21 to 23. I have no idea what that means for me since my Jeep is a 1991 and the donor NP231 came out of a 1991 and it's a 23 spline.
- There were a couple input shaft lengths
- I *think* my transmission is an AW4 since it's one of the only automatics I can find much about for the XJ
- All this gets more confusing when the NOVAk website says the T-case behinds the AW4 is usually a 21 spline...