Replace NP242 with NP231?

FRO · Dec 8, 2004

Hi!

I have a -90 XJ 4.0L Limited with AW4 and NP242.
I have ordered a 8" lift kit from Skyjacker, SYE-kit, 4.88 gearing and ARB Lockers (both axle). I will repace the Dana 35 with a Ford 8.8.

My question is:

I want to replace the NP 242 with a NP 231. I do not know what kind of splines I have. What car and years can i get the NP231 from?
If the splines on the t-case do not match my AW4, is it difficult to change the splines either on the AW4 or the NP 231?

Frode

NCSUcherokee · Dec 8, 2004

Is the SYE kit you already ordered for a 242 or 231?

A 231 can be had from just about any XJ/MJ or YJ/TJ. i dont know the exact year they started, but it was somwere around 87. Your 1990 AW4 is a 21 spline output, so it would be easiest for find a T-case with a 21 spline input.

FRO · Dec 8, 2004

NCSUcherokee said:
Is the SYE kit you already ordered for a 242 or 231?

A 231 can be had from just about any XJ/MJ or YJ/TJ. i dont know the exact year they started, but it was somwere around 87. Your 1990 AW4 is a 21 spline output, so it would be easiest for find a T-case with a 21 spline input.

Thank you!
I have ordered SYE for the 231.
What years, engine and cars have a 21 splines NP231?
Is it hard to change the the spline input on a 231? Or is it other mods I can do to make the 21 splines AW4 fit a 23 splines NP231?

NCSUcherokee · Dec 8, 2004

From what i have read, early AW4(<91) and BA-10 trannys had 21 spline outputs, and everything after that and all AX-15 manuals had 23 splines.

As for changing the output/input shafts i belive it is posible, but have no first hand experience with it so i will let someone else handle that one.

FRO · Dec 8, 2004

NCSUcherokee said:
From what i have read, early AW4(<91) and BA-10 trannys had 21 spline outputs, and everything after that and all AX-15 manuals had 23 splines.

As for changing the output/input shafts i belive it is posible, but have no first hand experience with it so i will let someone else handle that one.

OK!

Anyone? from what car, engine or year can I get a 21 splines NP231?
Is it i difficult to change the input/ output shafts?

043500 · Dec 8, 2004

All 4 cylinder jeeps (XJ, YJ, TJ, MJ) had 21 spline inputs for the entire line. The 6 cyl jeeps had 21 splines up through '89-'90 or so ...whenever the AX-15 replaced the peugot.

FRO · Dec 8, 2004

Great!

Now I'm close...

What about changing the shafts?

I got my hand on a 23 splines 231 in very good condition..

Flyfisher · Dec 8, 2004

Just call me curious...but why do you want to replace the 242 with a 231? From my perspective, the 242 has everything the 231 has, and more (full-time 4x4).

FRO · Dec 8, 2004

Flyfisher said:
Just call me curious...but why do you want to replace the 242 with a 231? From my perspective, the 242 has everything the 231 has, and more (full-time 4x4).

My car is only for offroad-use. It has no number plates, and will never run on public roads. The NP 231 is stronger, easier to mod, and the SYE-kit on stock in Norway is for the 231...

techno1154 · Dec 12, 2004

Is there such a thing as a NP231 that is gear driven; ie no chain? I am think I have heard this some time before.

iroc86 · Dec 13, 2004

techno1154 said:
Is there such a thing as a NP231 that is gear driven; ie no chain? I am think I have heard this some time before.

I don't see why there would be. One of the fundamental traits of the '231 is its chain-driven nature. If New Process/New Venture decided to make a gear-driven aluminum-housed transfer case, it's unlikely that they'd keep the same model number. There may be a way to convert it to a gear-driven unit via aftermarket parts, but I'd be curious as to why.

Just my two cents

.

Wiley Coyote · Dec 14, 2004

techno1154 said:
Is there such a thing as a NP231 that is gear driven; ie no chain? I am think I have heard this some time before.

No, there is not a gear driven version of the 231. There is a heavy-duty version that they used in Dodge trucks (don’t remember the years). It has a wider chain/sprockets and you can order them as replacement parts from places like Teraflex, Tom Woods, etc.

Replace NP242 with NP231?

FRO

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