np231 swap

[jstlink]

i have an 89' cherokee.4.0l,aw4 trans,np231 t case. i recently purchased an np231 t case with the 4.0 tera low kit installed.it has a 23 spline input and came out of a 90 something cherokee. i was told i have to change my trans as well due to the fact that my current trans has a 21 spline output.he did sell me the trans as well that would match up to it.so...2 questions,#1-is it true that the later aw4 trans had a different spline output than my 89'? #2-if so and i do have to swap the trans,will all my existing flywheel,etc. bolt right up to the later model trans to fit into my motor as well as all the wiring? hope this makes sense.thanx for any help. jon

[DaffyXJ]

Yes there were/are 21 and 23 spline AW-4 output shafts.
Can't speak the compatability of 89 to 91+ swap, as I haven't done it. But they should be close.

[5-90]

As long as your new case is early 1990's (1995-back, I think - search to be sure. This came up in a recent thread of mine on AX-15 swaps..) you should be able to just change the input gear from your old case into the new one, and then bolt the new one up. The cases are otherwise compatible - the NP/NVG transfer case mounting pattern has become an industry standard (which was derived, I think, from the Dana 300...)

Refer to your FSM for procedure on swapping the input gear...

5-90

[jstlink]

so your saying to try first switching out the input gear from my old t case(which is 21 splines) to the new t case,that way i don't have to change the tranny at all?

[5-90]

so your saying to try first switching out the input gear from my old t case(which is 21 splines) to the new t case,that way i don't have to change the tranny at all?

Ayuh. Changing the input gear is probably going to be a lot easier than the transmission, especially if you don't have a donor lined up. Gives you a good chance to get the input bearing and seal as well - might as well, since you're there anyhow...

5-90

[jstlink]

ok....so i get this right.take my current 21 spline input off my t-case and install it into my newer tera low 4.1 np231 t case so it will match up with my current transmission?is it just a matter of the 4 bolts holding it on there,pulling it out and swapping it, or does it get more involved than that?it seems to me that would be the easiest way as well,just didnt know if they were swappable.the gent i bought it from didnt seem to think so.thats why i'm here to double check. thanx again.

[XJING]

Ayuh. Changing the input gear is probably going to be a lot easier than the transmission, especially if you don't have a donor lined up. Gives you a good chance to get the input bearing and seal as well - might as well, since you're there anyhow...

5-90
He has the tranny, same guy sold him the tranny that sold him the T/Cand told him they would have to be installed togeather to make it work, so bolt the new tranny and t/c to the motor and go. Its plug and play.
Good Luck

[jstlink]

you are right.i do have the tranny as well.i was looking to see if just changing the input splines was possible instead of having to drop the whole thing.but....my original question was to see if the later model trans would bolt right up to my 89' motor.as well,the newer tranny doesnt have the flywheel attached,so was making sure the current flywheel on my old trans would bolt up to the newer trans.if there is a way to just change out the tcase input shafts,i wouldnt mund going that route to save a lot of headache. thanx

[jstlink]

so it is plug and play,even all the wiring to the newer trans?

[5-90]

Geez - I must have missed that. Yes - just swap the tranny and tcase as an assembly, and you're good to go. The AW4 didn't change much, internally, over the years, and the only real external difference was that Chrysler integrated the transmission control electronics with the engine control goodies sometime in the 1990's (may have coincided with OBD-II, I'm not sure.)

5-90

[jstlink]

didnt change much except the output splines.just my luck.ok, tranny and t case swap it is.i'll let you know how it goes.thanx

[XJING]

Should be, I have a manual. But helped out on a swap with the AW/4 and a 242 from a AW/4 and a 231 and it was plug and play, I looked at Novak and it appears it should bolt right up and the electronics are the same.
heres the site
http://www.novak-adapt.com/knowledge/aw4.htm