Jeep Enthusiast Forums banner

HELP!!!! 91 NP231 tranfer case swap into a 2000 automatic with NP231

1K views 15 replies 7 participants last post by  Apostle 
#1 ·
As the title says I am trying to figure what all is needed to swap a NP-231 transfer case into a 2000 Cherokee with an automatic and NP-231?

The 91 np-231 is from a 4.0l with ax-15 trans.

The 2000 is an automatic with np-231.

I have searched and found that some have said the spline count is different between the two. I have also found that some are saying that all the t-cases with an ax-15 behind them have a 23 spline output. I would assume that the 2000 with auto would have a 23 spline output as well?

My good friend has the 2000 with a bad t-case and I have the 91 np-231 sitting around and was going to let him use that. I just want to know if he has to swap parts over. I know that the tailshafts are different, could we just swap the 2000 tailshaft assembly into the 91 t-case? Any help or info would be greatly appreciated, we are planning on doing the switch-a-roo this weekend.
 
#5 ·
It's not that bad. T-cases are pretty basic. If the input splines don't match. You can swap the input shaft from the bad TC to the good one. I think you could swap the tail section also. Could take the 2 cases and build 1 good 1 out of them.
 
#7 ·
OP stated:
"The 91 np-231 is from a 4.0l with ax-15 trans."

AX15 is a 23 spline output shaft.

"The 2000 is an automatic with np-231."

in 1991 the AW4 was upgraded to a 23 spline output shaft from 21... a 2000 AW4 is a 23 spline.

So I am wondering how you came up so positive it is a different spline?
 
#8 ·
What can be done about the Mech. vs Elec. Can you just switch the new electronic parts over to the older t-case, or is the shaft physically different on the two? Does anyone have any photos that will show the difference? I have tried to search and no one really details what year the t-cases pictured are.
 
#9 ·
It can be done but I don't remember off the top of my head if it is a direct swap. Last time I did was a while back and I ordered a Dodge housing and a long shaft drive gear, and it worked fine to replace the electric ... but it was because I didn't have a spare at the time to scavenge from.... easy enough to check, pull em and see. It will take you 10 minutes to verify. I think it will swap as the length is the same, and they both use a gear drive off the shaft...

look at page 24 here:

http://www.atlas-tc.com/instructions/atlas.pdf

just count your teeth, and index the housing on the mechanical with the index mark for the corresponding teeth pointing down for mechanical install, electric is centered and should drop right in....but again.. I am going off the top of my head here, so don't take it as gospel.
 
#14 ·
nah Green, no game... I could explain it all weekend, and it won't do any good until he reads what I wrote, and gets the right manufacture date with the right component.

I gave you the best advice I could, based on 27 years of fixing broken stuff, and now I am done...now it's up to you to run with whatever floats your boat.. hope it works out for you as easy as I think it will. need anything from me, pm me, I'll get back to you soon as I can..I'm going Jeeping.
 
#15 ·
I would think that the tailshaft housing would swap over. You may need to swap the output shafts as well for the speedo to work. What's bad about his NP231? You could probably swap most of the internals over.
 
#16 ·
you can swap it over. everything can be changed to make what you need: input, tail, internals, and yes speedo. ive done it. took a 21 spline 231 with cable and turned it into a 23 spline with elec.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top