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Np231 info

S

SnowMexican

NAXJA Forum User
Location
Calgary Alberta
First I have to apologize cause I know this has been covered somewhere but I can't find the info I need. I'm finding mixed info everywhere..

I am swapping out a bad 242 for a 231. I have a 1995 auto. I have read about the 23 spline and the early models having the vacuum lines for front axle. But I'm confused about the tail shaft housing and what all I need to complete the swap, just the case or do I need the linkages, speedo cable and everything? I found a case from a 1999 but want more info before I buy it. Will I need a new drive shaft from a newer xj?

Again thanks for any info, or even just a pointer in the right direction.
 
Rear driveshaft is the same for 242 and 231. However they are different for 94-down and 95-up. Vacuum lines on the 231 were only for 1990 and older. Stay with 95-up NP231 and everything will bolt right up. You may need to swap speedo sender, but that's about it.
 
ehall said:
Rear driveshaft is the same for 242 and 231. However they are different for 94-down and 95-up. Vacuum lines on the 231 were only for 1990 and older. Stay with 95-up NP231 and everything will bolt right up. You may need to swap speedo sender, but that's about it.
Click to expand...

Thanks for clearing things up for me, appreciate it!
 
His info is spot on. The only difference in rear driveshaft lengths is form the rear axle differences. There is a great sticky in the FAQ's with all the different DS lengths.
 
you will need to change the shift gate and bezel.

the 4wd indicator will need the wiring spliced.

depending on the donor T-case you may need a longer or shorter input shaft. but you should be able to swap the one from your case.
 
If you think you may need to open up the 231 before you install it you should look into installing a slip yoke eliminator.

Sent from my SM-G930T using Tapatalk
 
Sorry I mispoke! The rear output changed in 96 and not 95. You will want to find something from 91-95 for maximum compatibility. Prior to 91 there were differences in the input shafts with some transmissions, easier to avoid that stuff by finding a 231 from a 91-95 with the same transmission
 
pretty sure you can just swap your input gear from your 242 into any jeep 231 and have it bolt up. The difference in 231s being the tail cone, as said, and the clocking position depending on what it came out of.

New process/new venture cases are a lot like Legos. One example that comes to mind is when I swapped a 242 into a WJ with a 247 in college. Had to tear both completely apart to swap the input gear from the 247 into the 242. There at some nuances when talking internals... Wide chain, 6 gear planetaries, SYE, etc... But swapping your input gear into a 231 of your choice should be fairly strait forward.

With that said... 231s with the features you need should be plentiful.
 
Last edited:
VAhasnoWAVES said:
pretty sure you can just swap your input gear from your 242 into any jeep 231 and have it bolt up. The difference in 231s being the tail cone, as said, and the clocking position depending on what it came out of.

New process/new venture cases are a lot like Legos. One example that comes to mind is when I swapped a 242 into a WJ with a 247 in college. Had to tear both completely apart to swap the input gear from the 247 into the 242. There at some nuances when talking internals... Wide chain, 6 gear planetaries, SYE, etc... But swapping your input gear into a 231 of your choice should be fairly strait forward.

With that said... 231s with the features you need should be plentiful.
Click to expand...

Be careful with that. I've heard the gear cuts changed at some point too. May have been the same time they went from 21 to 23 spline.
 
i recently swapped a 231 out with a 242. i had a 21 spline input on my 231 so i had to swap that into the 242. but other than that it fit like a glove. i did swap the tailcone? the part with the rear seal between the 2 as the 231 had a new seal on it.

the 231 was from my 88
the 242 was apparently from a 94
 
VAhasnoWAVES said:
which gear? there are a lot of gears in a Tcase. lol.

are you referring to the planetary gear/ring gear tooth change?
Click to expand...

the cut of the gears on the low-high planetary was changed in 94. older gears had square teeth, later gears had sharp teeth. The gear cut is on the input shaft, the pinion gears, and the annulus gear that's pressed into the housing. They all have to match
 
in my application i had to seat the bearing in the input gear slightly lower. but should work fine. but if you get a 231 from a 91-95 xj it will bolt right in no problem.
 
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