np231 out of 88 YJ

I have the opportunity to buy a np231 SYE equipped t-case out of a 88 YJ. Will this transfer case work with my 99 XJ? I havent found any issues with this swap so far, but figured id post to make sure.

That will be a 21 spline input. 23 didnt start till mid89 behind an AX-15.

You could however swap the input gear to 23 spline, i did this with an 88 YJ transfer into my son's 95 YJ. Used a 23 spline input from a 94 231.

i currently have a non-sye np231. I do have a SYE to put in, i just figured for only $75, i could get this already SYE equipped tcase and save some time. if i have to swap out the input, i suppose i might as well just mod my current case eh?

Indeed. If its got a really good SYE in it, you could move that over to your case and save the expense of buying one new.

In your shoes, I'd buy one new.

OverlandXJ said:

That will be a 21 spline input. 23 didnt start till mid89 behind an AX-15.

You could however swap the input gear to 23 spline, i did this with an 88 YJ transfer into my son's 95 YJ. Used a 23 spline input from a 94 231.

Click to expand...

Overland I had planned on doing this swap for some time, swapping a 242 from my 87 into my 93 with a 231. I actually bought a donor 231 from my dd era to get the input gear out of it so I could do the swap in my shop and not have any down time on my dd. However I found out very recently that the speedo will not work. The 87 has a cable drive and the 93 is something else, how did you solve this problem? Not to hijack but I thought it was pertinent to the op. Is there a speedo problem when going pre 91 231 to post 91 231?

Thats easy tk... just swap the speedo housing you need. Note the stem length on speedo gear coming out of the case you'll be using. The other is electriacl.

Also, on the input from 231 to 242 carefully check the meshing of the planetaries into the outter ring in case half. That outter ring can be swapped by removing the very large snapring. Just check before you button it up.

Thanks overland, I have already swapped the input shaft from the 21 spline that was in it to the 23 that I need, so I think I know what you mean about the outer ring, but I'm not sure about the speedo housing, I'm assuming this is the part where you swap the little plastic gear for speedometer adjustment for larger tires? Is it that easy do you think? I never heard of this problem before recently and am afraid I'll have to abort the mission of a 242 in my dd. I havent found any info on this problem. Are you positive or assuming? I may start a thread on this. Keep an eye out for it. Thanks for the help.

Yes, the housing that the speedo gear attaches to. You'll see where one has the capability for a speedo cable to screw to it, and the other type to simply attach a wire harness.

I swapped the speedo housing from cable to electrical (88 242) when i converted my 94 XJ to 4wd.

yes I found that in one of my saved threads also, thanks tonnes overland, appreciate the help, by the way, were you happy with the switch?