231 differences: TJ vs XJ

hear

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Is there a thread out there or other document that details the variances between the 231 on the Cherokee (98-2001 specifically) and what came in our TJ's?

I have a 231 out of a 99 XJ with a broken output shaft, and the output shaft from when I did the SYE on my 97 TJ. I'm not worried about being able to put the TJ output shaft into the XJ case, but what I don't know what sort of mating issues there are on the input side (or any other issues for that matter). I believe there is a difference across TJ's on manual vs. auto on the input shaft length, so I figure it's likely there is an XJ variance as well.
 
I tried digging through the parts catalogs from 97-99 TJ and XJs but they were ultimately not very helpful.

Some basics:

  • All 90s and later AW4, all AX15, and all 30RH/32RH are 23-spline outputs.
  • AX15 only required a short t-case input gear, but medium or long could be used
  • 30RH/32RH required a long t-case input gear, or an extended seal from Teraflex or similar.
  • Not sure what AW4 had, but it seems to be either short or medium from photos.
I know for sure that in the YJ days, and early TJ days (1997ish), they used a short input for manuals and long input on 3 speed autos. Somewhere in there, they started shipping all the TJ NP231s from 1998-99ish and onward with the long input, whether it was going behind the auto or manual. The manual was fine with the longer input, it just didn't require it for sealing purposes.

The parts catalog doesn't really help with any of this. The TJ 97-99 catalog lists one part number, 4796965, and calls it out for ER0 (4.0L) and EP0 (2.5L) with automatic transmission. The XJ parts catalog calls out that same part number as being for Magnum 2.5L SMPI with all automatic transmissions. So I honestly don't know there.

If you are needing to build a t-case to go behind a 30 or 32RH, use a long input gear. If it goes behind an AW4, you'll need to research more what goes behind them. I can't find too much for-sure info on that, BUT it does seem like they used a short based on eBay photos. So look more into that. If it is going into an AX15 or NV3550, a short will work, long can also work on the AX15, not sure on the NV.

I can't think of any other differences that would exist in the t-case. They were setup for the same drivetrain characteristics by the late 90s, so they both have no synchronizer, no vacuum CAD, etc. When you get to the older cases like 92 XJ and earlier, then they start to have the CAD switch, synchronizers, cable speedometer gear setups, etc. By the late 90s they were pretty much figured out and no longer changing things.

FYI, if you need to buy an input gear to make something work for your needs, pay attention to the gear cut and bearing width. Early-cut models were a more squared tooth tip and they had the wide bearing. They went til about the end of 1994. You do not want that for any of your late-90s cases. Late-cut were a more rounded tooth into a sharp tip, and they had the narrow bearing. So make sure you look for the late/narrow bearing keywords to choose the right input gear for your needs, if you have to buy one.
 
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Well, most likely I’m going to assemble it to sell it. Just wondering what I should disclose in the listing. And after all your research, I’m still not sure!
 
Well, most likely I’m going to assemble it to sell it. Just wondering what I should disclose in the listing. And after all your research, I’m still not sure!

Is this a t-case torn apart that you're just reassembling to sell? Using a long input, if you have one, would work for the most buyers. I'd market it to TJ owners probably.
 
Is this a t-case torn apart that you're just reassembling to sell? Using a long input, if you have one, would work for the most buyers. I'd market it to TJ owners probably.

It’s assembled, but I have to open it up to replace the shaft. It’s already been opened up (recall that thread where I showed the sheared off output shaft?), but it’s currently reassembled.
 
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It’s assembled, but I have to open it up to replace the shaft. It’s already been opened up (recall that thread where I showed the sheared off output shaft?), but it’s currently reassembled.

I see. Take some pics of the front side, or I can go try to find that thread and look, but a quick look would confirm mostly what it would fit. Like said earlier, in the later years it really just comes down to input length and not really anything else. Both XJ and TJ have double cardan front shafts. Both spin the front full time from the live front diff. Neither have a synchro. Pretty much all function is the same. Mid 90s and older gets dicey.
 
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I’m not worried about function, I know how this one operates. Really it’s just the input/output compatibility across years/models that I want to understand.

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