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NP231 ???'s

Frank Z

Frank Z

NAXJA Forum User
Location
Colorado Springs
Is there any difference between a 231 used with a Manual tranny vs. Automatic? I need to replace my 231 and am trying to rebuild a donor unit so I can yank the existing unit and stuff the new one in. I have not picked up a rebuildable case yet and don't want to waste time and money getting the wrong one. At this point I know I need a case with a 23 spline input.
Any info would be greatly appreciated.
 
Cases are the same...As long as you match the 23 spline.

Cases are the same on the t-cases from Ford, Chevy, Dodge, and jeep...As long as they are 231s from what I have read.

Just make sure you get the spline right.
 
From what I have seen.

The tranny output shaft and the tube between the trans and t-case are usually the differences. The t-case has 6 studs/bolts that mait to the tube between the tranny and t-case.

The short..t-case is always the same. Flat surface with input. Tranny, trans output shaft, or tube are the things that change for length etc.
 
Bouncy said:
Cases are the same...As long as you match the 23 spline.

Cases are the same on the t-cases from Ford, Chevy, Dodge, and jeep...As long as they are 231s from what I have read.

Just make sure you get the spline right.
Click to expand...

THEY ARE NOT IDENTICAL the input for the manual is longer than the input for the automatic. A manual 231 will not bolt up to the aw4 !
 
Bouncy said:
Thanks for yellin in on that one.

I have not seen manual or auto be any different. Thats my story and I'm stickin to it. :p
Click to expand...

LOL, Just enough to bind up the TC......about 3/16" longer.....dont ask how I learned that one
 
I have a 93 XJ auto. I put in a 231 from my parts xj (also a 93, but it's a manual). No ill effects here other then the fact that the bushings in the linkage are out of round. Been running it for months now. Was a direct swap.
 
Stick-out lengths of the input shaft vary by trans application; however, the input shafts are interchangeable.
Don't know variances by application, but I have seen drawings showing the differences, so find out what your "stick-out" is, and measure the donor unit to determine compatibility, or include a new, correct input shaft and bearing in your build-out plans.
I put an NP231 out of a '92 AX15 (23 spline) equipped Wrangler into my Peugeot (21 spline) equipped '88 XJ; had to change out the input shaft and front bearing. Other than that, it was a direct bolt-in.
 
Frank,

Call the guys over at Novak conversions, there are actually three different lengths of NP231/242 input gears in the 23 spline flavor. At one point, I had the "long" input gear, and it wouldn't work with my 242 (no longer trying that one) with my manual tranny. So in talking to Novak, AW4's could have either the "medium" or "short" gear, and manuals could have either the "medium" or "long" gear - in a nutshell, its tough to tell what you need without pulling your case and measuring your input gear exposure - Novak can probably provide more clarity than I just did...:(
 
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