question about automatic transmissions and transfercases

so i was replacing my transmission today in my 90 jeep cherokee untill i ran into a a problem

first off its a 90 cherokee automoatic 4x4.

i was planning on transfering the transfercase from the old transmissio to the new one untill i realized the splines on the transmission(i think its the output shaft) are a different size and the transfercase will not fit

the transfercase on the original transmission was np242 i think so does that mean that the new tranny needs a np231?

can i just move one shaft over to the new transmission?

thanks

The spline count of the output on the AW4 (that's the auto you have) changed around, I think, 1990/1991 from 21-spline to 23-spline.

Yes, you can swap the input gears - but between same models (NP231-NP231 or NP242-NP242.) I don't think that the input gear would swap between the NP231-NP242 or the other way about - but I've not been able to confirm that.

You can drop the NP242 in, I think the same linkage is used, you just have to remember the extra position available in the NP242 that the NP231 doesn't have. (Or the other way around.)

If you decide to swap the input gear, I know that the input gear cut (the helix angle) changed sometime around 1994 or 1995 - I don't know about the NP242, but the same thing probably applies. So, make sure you get an input from the same bracket as your existing transfer case if you want to swap.

Short form? You can bolt either the NP231 or NP242 to the AW4, as long as the spline count is correct. I'm fairly sure that the break point for that was 1990/1991 (21/23-spline,) but a brief search here should turn up a confirmation for that.

but with an AX15 I think 1989 1/2 went to 23 spline

i have a np242 transfercase i want to put on a transmission i guess is for a np231...can i do a straight swap of the input shaft???? or do i have to get a np231 for that transmission???

is it a straight swap is there anything i need to be worried about?

thanks

the 231 is better IMHO

veedubshafer said:

but with an AX15 I think 1989 1/2 went to 23 spline

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That's coicident with the shift from the BA-10 (21-spline) to the AX-15 (23-spline.) Point - I think all of the Aisin gearboxes were 23-spline, so the AX-4 and AX-5 that were used on the four-cylinder were 23-spline as well (while the BA-10 was being used.)

can i just swap the output shafts on the transmission??

or do i need to find a bigger input shaft for the transfercase??

blazinjames said:

can i just swap the output shafts on the transmission??

or do i need to find a bigger input shaft for the transfercase??

Click to expand...

It would be easier to swap the input shaft on the transfer case - automatics tend to be loaded from the front, and swapping the input shaft means you're going to tear the thing totally to bits...

You can find 23-spline input gears with a little looking, you can probably find them new from Novak, or you can just swap the transfer case entirely to the correct spline count. Just note the donor year of the new transfer case, if you have to overhaul the thing in the future (recall the change in input gear cut I mentioned earlier...)