4x4 Conversion with NP242. Clarification needed.

[Minuit]

I'm starting to think about my upcoming 4x4 swap on the '91 (2wd AW4 4.0), and I've decided I want an NP242 transfer case for the full time option. I know there is some debate about whether or not the NP242 is as good as the NP231, but this is a lightly used street driven truck that will never, ever be wheeled hard. I don't need 4x4, but I want it. I want it bad enough to spend hundreds of dollars and many hours crawling around in junkyards to get it.

 

I've done a little bit of research, but I have a few questions. Can someone fill in the blanks? I want to have a complete list of everything I'll need before I start buying anything, and I want the swap to go as smooth as possible once I've started.

 

Here's what I think I know. Please correct me if anything I think I know isn't correct.

 

- I'll be using an AW4 between the years of 1991 and 1996. According to my research any 91-96 AW4 will be bolt on to my '91 truck without any other changes.

 

- The transmission output spline count changed in 1991, so a Renix era NP242 won't fit an HO era AW4.

 

- ZJ NP242s seem more common than XJ NP242s. Will a ZJ transfer case fit behind a 91-96 AW4 if I can't find an XJ NP242? This is my main question.

 

- WJ transfer cases don't have the speedometer hookup on the transfer case, as they used the ABS wheel speed sensors for the speedometer signal. I assume this rules out WJ transfer cases completely.

 

- There was a major change to the NP242 in 1994, so do the transmission and transfer case need to be on the same side of that year split? If a ZJ NP242 will fit at all, which years of AW4 will it fit?

 

- What about 96-01 XJ NP242s?

 

I want to do this using only factory parts (except for possibly the shifter linkage) that I could reasonably expect to find in a junkyard. I would rather not swap transfer case parts to make this work. Once I get this straightened out I promise I'll make a big huge writeup to make this less confusing for people who decide to do this later on :D

[Marine1Texas]

I use a 242 on my 87 mj. I have it in either 4L or now 2L with conversion all the time. I will pull a 10,000 pound trailer 100 acres some times thru the mud on my land, I have no problems with it. I but a few time ever drove it in high on the road, but when it was snowing. I have had more trouble with my d44 chipping teeth ever then my tranny or transfer case. 

[dragordie]

242 T/case is what I have ran or swapped into all my last 3 ZJ truggys I have built. Also its what is in most H1s. On the H1s they add cooler lines like an automatic trans has. Add a Hack n tap and your ready to go. I personally like the 242 not a lot of aftermarket goodies like 231.  This is the T/case which is in my Rock Frog MJ  

[yxmj]

I run a 1998 xj 242 in a 92 YJ behind a stroker with 33" tires...i love it.
Sorry all my conversions where with ax15's so I am not up to speed on aw4 spline count.

 

There are others on here who have done it 

[Hippie66]

Ran a 242 on my old XJ. Abused it hard enough to split the case once, still got me back home. Swapped in another 242 and wheeled it hard that night.

[oldseddie]

If you don't already have one, get it from a 97-01 Cherokee or GC as they shift a lot better. Daimler Chrysler really worked everything over for vibration noise and harshness.

 

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[schardein]

I had one in an 89 XJ wagoneer I used to own and loved it.  I have a 1991 242 (23 spline) sitting in the garage with the same plans as you, a 4wd conversion with an AW4.  I plan to use a boostwerks shifter as they seem to have great reviews.  However, I did recently remove, free up, clean up, lube and re-install the 231 shifter in my XJ, and it made a world of difference, so not sure it's worth the expense for aftermarket.

 

You probably know the 242 uses a different shift bezel, and also a different shift gate (than a 231).  So grab that stuff when you get the case.  I have some spare 242 shift bezels if you need one (and maybe a gate, have to look...)

 

The later 242s use a different design rear output shaft.  My research shows a ZJ 242 interchanges with a XJ 242.  Didn't know of a change in 1994.

[gogmorgo]

The 242 (also 4.0 and aw4) in my MJ came out of a '93 XJ used for plowing snow. Seems to have held up just fine. I've been ripping around in snow a couple feet deep over the last week, donuts, etc, in full-time and haven't broken anything yet. As far as the reputation goes, yes, they have a reputation for failure, but I would also argue that because of the full-time option the chain and everything gets significantly more use than a part-time case does.

Everything for the '93 into '91 swap was plug and play, except a little bit of wiring confusion with the 4x4 lights due to the change from a CAD to non-CAD setup. And my '91's early speedometer assembly went right in in place of the '93's.

If you can find one, as with any 4x4 swap, it's probably best to pull everything from the same donor to ensure compatibility. My (mostly) mechanically sound but rotten-body donor cost $300.

For better on-road performance, you'll also enjoy upgrading to CV axle shafts.

[Minuit]

Okay, so after some more frenzied Googling I've come to the conclusion that the input gear is the main factor in compatibility between transmissions and vehicles. Post 1990 AW4s have a 23 spline output, but there's different lengths of transfer case input gears too.

 

I've found this chart on Novak. The only problem is it creates more questions. It does mention that the 1994 change was internal to the transfer case, so my thinking is that it wouldn't affect compatibility?

 

(23 spline only)

Short Input

30RH

32RH

AX15

 

Long Input

TF904

TF999

NV3550

NSG370

 

Medium Input

46RE '93-'95

AW4 post '90

 

The '94 ZJ is unique in addition to all of this.

 

Supposedly the medium length input is rare. How is it rare if every post '90 AW4 (in addition to 2 model years of V8 ZJs) uses a medium length input gear, or is this an error in the chart? If the chart isn't correct, which length transfer case input gear does the AW4 use? Some sources say the AW4 uses the short input, can anyone confirm? What about the ZJ transmissions other than the 93-95 46RE?

 

Thanks for all your comments and good to know that they can stand up to some abuse. I'll never run mine that hard, but good to know it can take it.

[shelbyluvv]

Your list is spot on. I have a 242 in both of my trucks. Even the V8 truck. My V8 has a 46RH trans and it was a long input 249. I took the input out of the 249 and put it in my 242. Easy days as blown 249s are a dime a dozen.

 

https://kevinsoffroad.com/249-to-242-swap-instruction-guide

 

is a great resource

[xjrev10]

242s are just as common or even more common then 231s up here. (MN)

[Minuit]

Down here where we don't get very much snow I see about 15 231s for every 242 sadly, at least in XJs.

 

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[Wiggilez]

Sorry for the thread hijack but since we're all on the topic will my 1990 ax15 bolt up to my 1990 242 which came out of an automatic xj?

[Blue88Comanche]

Sorry for the thread hijack but since we're all on the topic will my 1990 ax15 bolt up to my 1990 242 which came out of an automatic xj?

as long as it has 23 splines you should be good. I don't recall when the aw4 went from 21 to 23 splines... the input shaft length required is different for the ax15 and aw4, but I bolted mine on anyway and haven't had any issues.

 

 

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[mvusse]

I got my daughter's 96 XJ as a 2wd. I used an 4wd 0AW4 transmission out of another 96 XJ (for you I would stick to 91-95, partway through 1996 the model year they changed things, including the plug on the CPS. I also don't know if the TCU or transmission are any different to work with the OBD II ECU, so better safe than sorry.

 

I used a 1993 242 out of a ZJ, with a hack-n-tap SYE. The transfer case I got was missing the tab that bolts onto the transfer case for the shifter, so I got one from a 231. Bad move.

 

The tab on a 231 is longer and on a 242 will not allow full range of movement. This caused the case to only be partly in 4wd-low, which in turn cost me the center differential over 12 months of use. You will need the 242 specific shifter tab, and shift gate. Everything else will work with 231 parts.

[Wiggilez]

 

Sorry for the thread hijack but since we're all on the topic will my 1990 ax15 bolt up to my 1990 242 which came out of an automatic xj?

as long as it has 23 splines you should be good. I don't recall when the aw4 went from 21 to 23 splines... the input shaft length required is different for the ax15 and aw4, but I bolted mine on anyway and haven't had any issues.

 

 

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cool, now if only my MJ wasn't covered in snow.

[mvusse]

 

 

Sorry for the thread hijack but since we're all on the topic will my 1990 ax15 bolt up to my 1990 242 which came out of an automatic xj?

as long as it has 23 splines you should be good. I don't recall when the aw4 went from 21 to 23 splines... the input shaft length required is different for the ax15 and aw4, but I bolted mine on anyway and haven't had any issues.

 

 

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cool, now if only my MJ wasn't covered in snow.

 

 

Didn't the automatic go from 21 to 23 spline at the same time they went from the BA10 to the AX15?