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NP231 swap out

4K views 18 replies 7 participants last post by  YJJPWrangler 
#1 · (Edited)
Hey i busted my NP231 the other day(put a hole in the rear of it) and i was gonna switch it to my friends NP231 that came out of his 94 cherokee. Mine came out of an 87 Wrangler. Mine has a vacuum line and his is electrical. Is this a problem? Can i mate my front half with his rear half?
Also, im getting a SYE as part of the deal. Whats the best driveshaft to go with?

Zack
 
#2 · (Edited)
the 94 will have the incorrect input shaft for your 87 tranny. You should be able to swap your input shaft to the 94 t-case. The vacuum switch will most likely be able to be unscrewed from the 87 case and screwed onto the 94 case. That vacuum switch only powers your front axle disconnect anyway. In theory you should remove the vacuum from that axle anyway and either build a cable-lock setup, or install TJ shafts (or swap that axle out completely).

edit: for driveshaft, there are two major sponsors on this board... JE Reel and High-Angle. You could of course always go to a local driveline shop as well.
 
#4 ·
YJJPWrangler said:
why would the xcase from the 94 have a different input shaft? Also I'm not really technical on trans cases. Is the input shaft the shaft that goes into the transmission? Also if i did have to switch input shafts...how much is one?

Zack
The 87 t-case should have a 21 spline input shaft whereas the 94 case has a 23 spline input shaft. You would take the input shaft out of your 87 case and put it into your 94 case. Yes the input shaft is the part that goes into the transmission. Honestly I'm not sure you should be doing this part on your own if you don't already know what an input shaft is.
 
#7 ·
ok thanx man...i think we will tear it apart on wed...i really don't want to tear both of them apart and mate them together...so i should just change the input shaft right? (sorry, i need confirmation, its my dd and i need to get it back on the road) Thanx again

Zack
 
#8 ·
the case from the 87 wrangler is not a np231 it is a np207. just so you know.
 
#9 ·
offroadmission said:
the case from the 87 wrangler is not a np231 it is a np207. just so you know.
crap... I'm glad you were paying attention. Somehow I remembered the 21 spline, but not the fact that it was a 207.

ok, yet another question to ask... is your friends case from a 4cyl Jeep? If so it should actually bolt in, if not then you will need an input shaft from a 4 cyl Jeep 231.
 
#11 ·
YJJPWrangler said:
nope...it says NP231 AMC so im guessing it was one of the last production models for AMC. I have the 4.2 I-6 in mine and his jeep had a 6 in his too. cant i just switch input shafts?

Zack
never heard of an NP231 AMC,seen an NP231J

I have no idea which input shaft your 6 cyl will have 'cause I never heard of an 87 with a 231. What tranny you got?
 
#12 ·
correct me if i'm wrong.....but wasn't the yj the first jeep of the chrysler era?
therefore no amc.
 
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