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Discussion Starter · #1 ·
What modifications, if any, will be needed to swap from an NP231 to an NP242 transfercase??

My NP231 is married to the AX15 manual and the NP242 is coming out of a much older automatic (in the tree).

Any and all information would be great. Thanks again all!!

-Semper Fi
 

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Greetings from veteran submariner. :)

I’m doing this exact swap, and just finished rebuilding the transfer case.

To guide you better, I need to know year of your XJ, and the year that the 242 came from.

Typically , ax-15 uses a short input shaft on the transfer case for all years it was used with 23 spline input.
If the 242 came from a 1991 or newer, it theoretically will have a 23 spline medium input shaft. Having said that; I got my 242 from same year as my xj, and for some reason it had the 23 spline short input shaft as well (verified with micrometer).
If it came from 1990 or older , then it will have 21 spline , and you will need to swap to a 23 spline input gear. You can swap from your 231 , or buy a 23 spline to drop in.
One other factor- if you wind up changing the input shaft, there is early gear cut, and later gear cut (changeover was in 1994, but all 1995 and newer have later cut).

If you got the 242 from 1997 or newer, it uses different rear output shaft, and will need to change over the cone from 231 to it (or buy new one + seal for it - they still make them)

Other than that, I’d recommend getting the shift gate for 242, as well as the shift bezel (physically shows the mode you are in). I’ve also heard argument about using the 242 shift linkage; but some have said using the 231 can be done , just needs adjustments. I opted to go with aftermarket Azzys shift linkage - WAY less complicated and works with 231 or 242. There are other aftermarket kits as well that use cables.

For the speedometer gear, I’d just take the entire vehicle speed sensor from your 231 and drop it into the 242. Make sure to take picture of the orientation of the VSS before unbolting it!! Or else you will have to remove and adjust it til you find the right slot for speedometer gear to engage with the drive shaft .

The 231 dash light switch works differently than the 242. 231 has power and ground wires. When in part time mode, switch is tied to ground via the wires, to make the part time light go on.
The 242 uses transfer case as ground. Red wire goes to part time, and yellow/green wire goes to full time light. Part time ties switch to case ground on red wire. full time ties switch to case ground for yellow/green wire
What I plan to do is cut the black wire; then run yellow/green wire up same path to engine compartment , find the wire to splice it into at dash harness, and splice it. Will pass on info when I have exact info on where to splice.
You could also grab 242 dash wire harness, but would still wind up needing to do splice to bypass the ground and connect to full time.

The case itself is direct bolt on to transmission, as long as input shaft matches like said before.

A lot of info there, but once you have everything matching, it should be easy swap. And dash lights are nice but not required- you can look at shift bezel to see what mode it’s in.


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Discussion Starter · #3 ·
That is a lot of info, thank you.

Mine is a 98 and I believe the 242 is coming out of an 89/90. Good thing for parts is I have access to everything on the 242 donor, so there shoildn't be much I'll be needing to search for. Once I finish regearing my XJ to 4.56 I'll be looking to start the 242 swap. So this thread should be a lot of back and forth.

Thanks again!!
 

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Discussion Starter · #4 ·
The NP242 donor ended up being a 93 Cherokee XJ. The shop has removal scheduled for the 20th of this month. And I will be getting everything thats attached to it, literally everything. Do you recommend I also get something regarding dash lights you were referencing??

On a side note, I just found that my NP231's rear output shaft is bent...lmfao!! Wasn't noticeable until I went from 3.07's to 4.56's and having the driveshaft rebuilt.
 
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