XJ/TJ Transfer Case Compatability Question

Long story short, my roommate's tcase in his 99 TJ (NP231) took a dump tonight. It had been run dry on accident for an unknown amount of time this past summer due to a leak, and I guess that finally caught up with it tonight. Not sure what exactly let go, but there's now a fist size hole in the bottom of the front of the case (I can see in right to the chain).

Need to get a tcase ASAP and get this thing back on the road....I know the internals are the same b/w an XJ 231 and a TJ 231, but are there any years of the XJ 231 that are a direct bolt up? Anything to widen the search and try to lower the price...as the TJ cases we've seen online are running $350-$400.

From what I know so far:

99 TJ
2.5L 4-Cylinder
AX-15 (I think?)
21-spline NP231.

Any help ya'll can offer is much appreciated....it's been a long night:eeks1:

I'm pretty sure it would be an ax-5 paired with the 2.5L ... Sorry, but can't help much otherwise

1990-ish (23-spline input) should be the same. I know the YJ/TJ transfer cases are clocked differently (they sit flatter) than the XJ, but, IIRC, that's done with the transfer case adapter housing on the backside of the transmission (simplifying logistics.)

If you get the transfer case from a rig equipped with the AW4, make sure to measure the input protrusion and compare it to the case you're taking replacing. I believe that all of the NP231 used with the various manuals (AX-15, AX-4, AX-5) all used the same "stick-out" for the input.

You will need a 231 from a ax-5. It will be a 21 spline tcase also. When I went to a 94 2.5L in my 84 xj it was from a yj. The TJ IIRC used the same set up till the ditched the 2.5L jeep motor for the 2.46 Chrysler.

Awesome! Thanks a ton guys!

Good to know it's the AX-5...for some reason I didn't think the 15 sounded right for that year of the Wrangler.

5-90 said:

I know the YJ/TJ transfer cases are clocked differently (they sit flatter) than the XJ, but, IIRC, that's done with the transfer case adapter housing on the backside of the transmission (simplifying logistics.)

Click to expand...

So if i'm understanding that right, if we were to get one out of an XJ, it would still work via the adapter on the back of the transmission? Provided it has the correct spline count.

Never had to swap a tcase before...so this will be a learning experience for both of us.

UNCC_99XJ said:

Awesome! Thanks a ton guys!

Good to know it's the AX-5...for some reason I didn't think the 15 sounded right for that year of the Wrangler.



So if i'm understanding that right, if we were to get one out of an XJ, it would still work via the adapter on the back of the transmission? Provided it has the correct spline count.

Never had to swap a tcase before...so this will be a learning experience for both of us.

Click to expand...

Tim, I can throw in what little knowledge I have here. If you get one out of a TJ, you should be able to position it correctly behind the XJ's transmission, like 5-90 said, its as simple as bolting it up different than it was in the TJ, so driveshafts, etc will line up. Swapping T-cases is very easy, it can be done in under an hour if you have a 9/16" or 14mm Gearwrench, otherwise it may take significantly longer. I would drop the crossmember as well even though it's not always necessary. Let me know if I can be any other help.

UNCC_99XJ said:

Good to know it's the AX-5...for some reason I didn't think the 15 sounded right for that year of the Wrangler

Click to expand...

AX-15s did come in wranglers, but AFAIK never with the 4 cylinder, which got the AX-5. I forget what year, but the wranglers switched to the nv3550 at some point, doing away with the ax-5...

UNCC_99XJ said:

So if i'm understanding that right, if we were to get one out of an XJ, it would still work via the adapter on the back of the transmission? Provided it has the correct spline count.

Never had to swap a tcase before...so this will be a learning experience for both of us.

Click to expand...

Correct - as long as the input shaft is the same (spline count, and stick-out if you get a donor from an AW4,) you'll be fine.

Swapping transfer cases isn't terribly difficult - but I do advise you to get a set of "stubby" wrenches - or at least a 9/16" stubby. It makes it easier to get at the two nuts on the top of the thing. If the AX-4/5 is anything like the BA-10 and AX-15, you won't be able to get a socket on there, and you'll only be able to drop the transfer case so far before you hit something - either remove the transmission/transfer case as a unit and swap the tcase on the ground (which is a pain to get back into place,) or use the right tool and swap just the transfer case (which cuts the weight you'd have to handle by about two-thirds.)

A "stubby" wrench in 9/16" is about four and a half inches long, and that helps you get into tight spaces. The torque on those nuts is not great, so that should be plenty (and you can always get creative if you need to apply more torque to break the nut loose anyhow.)

x2 on the 9/16 stubby. I got one at Harbor freight that was a 9/16, ratcheting, stubby, flexible wrench for $8 or so. Worked great, although it was still a pita.

Thanks guys...ended up getting one from another TJ for $200, and a friend of his who is going to be working on his own TJ is going to swap it out for him....which means I dont have to lay in the parking lot in the rain this week to work on it

I appreciate all the help...definitely learned a good bit!

UNCC_99XJ said:

Thanks guys...ended up getting one from another TJ for $200, and a friend of his who is going to be working on his own TJ is going to swap it out for him....which means I dont have to lay in the parking lot in the rain this week to work on it

I appreciate all the help...definitely learned a good bit!

Click to expand...

If you ever need stuff built or swapped let me know I have a friend in Concord that is a fabricator/jeep builder. He is very reasonable and does a great job.

Ghost said:

If you ever need stuff built or swapped let me know I have a friend in Concord that is a fabricator/jeep builder. He is very reasonable and does a great job.

Click to expand...

Definitely good to know! I'll keep that in mind, thanks!