I'll be on vacation for the uocoming holidays and will most likely be spending the entire time cleaning my garage. Give me a moment, and I'll finally crack open that 242AMG case and give you a definite answer on the mainshaft dimentions

 

Alright, we're getting more serious now. I want the manual swap done, so the NP242HD needs to be swap ready. There will be a bit of AX15 info in here as well but I'll try to keep the focus on the NP242HD.



Black Friday sales got me on a buying spree. I've ordered the IRO SYE kit, and the AMG 32 spline output shaft.

I've been doing research on the transfer case input shaft length. Novak Adapters has a bunch of info on this, but a lot of it seems to be incorrect according to the forums. I am going off the assumption I can't trust the Novak info. I'll link it anyways. The Novak Guide to the New Process / New Venture Gear Transfer Case Input Gears (novak-adapt.com)

For the sake of posterity, here are some pics.


Above is the input shaft of my NP242WJH transfer case, as removed from a 2001 V8 WJ. It's a 23 spline extra long output, that I see no documentation of on Novaks site - it sticks out 3" past the mounting face, not the 2.1" they describe as "long".


Above is an XJ spec NP242J. It sticks out 1.4" past the mounting face.I did not personally remove this from an XJ, but it was advertised as being from a 2001 Cherokee, the build sticker is from 1999, and it has a speedo sensor. That's a safe bet it's an XJ part.

I've never gotten a hold of an NP231 meant for a manual transmission, but this forum post has the answer I need.
AX15 Output Shaft and NV231 Input Shaft Lengths | Jeep Enthusiast Forums (jeepforum.com)



The above image was taken from the link - a 1997 TJ AX15 came with an NP231 with a 2.125" input shaft length.


Above is my XJ spec AX15, part number 52108047. It matches the measurements of his TJ spec AX15, The transmission output shaft sticks out 0.52".

To summarize what I've verified so far.



So what happens when we try to put all this together?


The 3" long input shaft will not work with an AX15. It has an interference of 0.8" or so (probably less). Subtract that from 3" and you get almost the exact length of the manual NP231 input shaft - 2.125"

Seems like Jeep used every bit of output/input shaft overlap they could get.

The way I see it, I've got three options, listed in order of preference.

1. Cut 242HD input down. Could do it Hack n Tap style, or get it cut down on a lathe.
2. Swap to the 242J output shaft, short length. Lose 30% of my spline engagement - not a huge fan, but I am sure it happens often with people looking to replace a broken NP231 on a manual.
3. Tear the whole thing apart, buy the correct input shaft. This project is already costing me way too much for what it's worth.

I was hoping I could get away with not tearing it down to the input shaft. We'll see.

 

The option you have sound correct. The guy I bought my HD case from attemped to do what we are, and swapped in the J shaft, so I have the unwanted spline length (which is how I came across almost ordering the AMG one. I would have if the ebay seller accepted returns). They never installed it because they ran the (detent?) in too far and couldn't cycle through the gears. His loss.

As far as cutting down the HD shaft, I'm not sure if it is cut for the speedo. I never had one so I am not sure. But if that is the case, that would be best financially. You could mount it in a vise and trim it with an angle grinder, mount it in the chuck of a drill press and trim it, or take it to your local machine shop. I don't think they would charge you any more than $50 for a single 10 minute cut.

I do not recommend the J shaft. Only because that what I have, and I saw how much spline is touching. I would seriously hate to see a rebuilt transfer case have to be done again just because there was little contact surface area.

I would definitely suggest the AMG mainshaft (if the measurements came out correct.