aw4 np231 spline count

Ok, I have searched 30 some odd pages and I think I came up with the answer to my ?, but I would like some verification.

I have a 1989 xj 2d with the I6, aw4, np231. According to my research I should have 21 splines. Is this correct?

What I am looking at is to start saving the money for an Atlas II. My tranny and tc are fine but I have upgraded most everything on my junk and the tc is one of the last big purchases I am going to make.

If I indeed have the 21 spline units should I try to find a 23 spline aw4 and purchase the Atlas with the 23 splines or will the 21 splines units sufice? TIA

Sorry, I maybe should have put this in Mod. Tech. Please move if needed.

yes, your AW4 is 21 spline unless someone swapped it. I've never heard of someone breaking the 21 spline output, but one advantage of the 23 spline is that it is much more common so your Atlas would have higher resale value.

I would ask AA how much it would cost to later go from the 21 to 23 spline, and shop for a 23 spline AW4, then go with whichever is cheaper.

I would also check out the STaK 2 and 3 speed t-cases.

BrettM said:

yes, your AW4 is 21 spline unless someone swapped it. I've never heard of someone breaking the 21 spline output, but one advantage of the 23 spline is that it is much more common so your Atlas would have higher resale value.

I would ask AA how much it would cost to later go from the 21 to 23 spline, and shop for a 23 spline AW4, then go with whichever is cheaper.

I would also check out the STaK 2 and 3 speed t-cases.

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Thanks BrettM. Is this the link to Stak? http://jeephorizons.com/news/stak_071305.html
Do you run the tc? I have a good friend that owns a local jeep yard. I could probably get a good 23 spline aw4 pretty cheap. Does anybody have any idea how much they are going for used off hand.

this is the Stak link: http://stak4x4.com/

i got a 96 23 spline AW4 with about 100k miles for I think a little over $100.

BrettM said:

this is the Stak link: http://stak4x4.com/

i got a 96 23 spline AW4 with about 100k miles for I think a little over $100.

Click to expand...

If you look for a newer AW4, keep in mind that it changed in 1996/1997. The rear sensor changed and will not work with your 89 TCU. You could swap the older sensor and internal rotor to make the swap work, but that entails pulling the rear off the tranny. I think you can swap in the newer TCU and harness, but I'm not positive that the ODBII and Renix used the same voltages for the TPS sensor? I have a 99 AW4 in my 89, but I took the unorthodox route of building an adapter to convert the rear sensor signal to what the 89 TCU was expecting.