tcase input spline count

The patient is a '90 4L AW4 with a pooched NP231. I've read many posts here and on other sites which say that the aw4 output/np231 input spline count is 21 for '90 and prior, 23 for '91 and up. I've also read here and there that '90 was a transition year so it could have a 21 or 23. Can anyone verify one of those statements? As well, if there is a possibility of having either spline count is there a way to tell without pulling it?

Calling around I've found replacing the entire case is cheaper than buying even just the chain so I think I'm gonna use this opportunity to swap in a 242. Since it's my dd I don't want to pull the tcase just to count the splines if it's not necessary.

cheers

I believe (don't quote me on this) but when they changed to the HO, they changed to a 23 spline. Just removed a 21 spline 242 in favor of a 231.

-Ron

The HO's ('91 and up) definitely have a 23 spline and '89 and prior definitely have 21 from what i've read.

Gotta go to the dealership this morning anyways and I'm hoping by looking up the available input shafts for a '90 on their system will confirm something.

well the dealership couldn't tell me anything. hell-after a half hour they still couldn't even find the parts on their computer! its up to you guys! guess if noone can confirm anything i'll just have to pull it and count.

The following case ID numbers use 23 spline input gears: 53006091, 53006094

And 21 spline: 53006093, 53006096

Source: http://www.quadratec.com/advisor/jeep_oem_replacement_parts/transfer_case/NP_model_231.php

Those are their notes for the 87-90 XJs

thx montanaman-I'll be checking it out tomorrow morning.