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T Case swap.


NAXJA Forum User
First off, Its been awhile since I have been on here. I have searched and have come up with mixed results for the answer that I am looking for.

I have a 1990 4 door XJ with a swapped in 87 4.0L with the original 90 AW4 Trans and T case. I believe that the original Tcase is going out.

I lucked into finding a wrecked high mileage 1993 4.0L HO with the AW4 trans and NP231 Tcase. Although it has 199k on it it was owned for the majority of its life by a friends grandmother who bought it new and had it serviced regularly. It was given to my friends sister who had it less then 2 years and she wrapped the rear end around a telephone pole. It does not smoke and shifts good and the 4WD was most likely only used minimally over the years and never abused.

I have been trying to find out whether I can just swap the T case in or if I am going to have to do more than that. I have read about the different spline counts and I dont really want to crack the cases and swap out the shafts.

I have scrapped out the body of the vehicle, however I kept the most important parts. I have the engine, Tranny, T case the Hi pinion Dana 30 front, radiator and the ECU.

If I have to do a major swap I might just swap the shortblock, tranny and Tcase all in. I would prefer to just do the Tcase.

Any advice on what spline counts are between the engine, tranny, and T case and what will work with what would be very helpful.

Thanks in advance for you help.
Renix = 21-spline , HO = 23-spline.
You can bolt the newer AW4+t-case in tho.
Well I guess I am going to have to pull the case. I would tend to believe that it would be a 21 spline because its a Renix. But....

Woody posted.

New Process NP231 Command Trac: 2-speed, chain drive, part-time 4WD. 2.72:1 low-range. 87-01 2.5l 4cyl and 4.0l I-6 models with manual or automatic transmission. 87-89 21-spline input, 90-01 23-spline input. The older models used a vacuum switch to activate the dash indicator lamp and engage the front axle disconnect. Newer (non-disconnect axle) versions used an electrical switch to activate the dash lamp. The shift indicator pattern is 2WD > 4WD high range part-time > Neutral > 4WD low range part-time.

So, that puts me in the 23 spline. I am getting ready to start this project and I hate to get part way into it only to have to rethink all my plans.