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Old March 18th, 2017, 12:08
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Kittrell Kittrell is offline
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NP242 Transfer Case Tech

There is a lot of good info out there on the options for the 242, but it is pretty scattered. I wanted to bring it all into one place. Now if you are like me you love the 242 for it's full time capabilities in the snow. However, if you are also like me then you like to take your XJ offroad. And that can present some difficulties depending on your budget and what you want the end product to be.

Let's start with the available cases. I will not list every application for these cases, but the main ones as it pertains to this article.

NP242 J (J for Jeep)
This is the case that comes in the XJ from the factory if you have the Selec-Trac 4wd option.
There are essentially 5 versions of this light duty case.

Early 21 spline input w/internal slip yoke, this came in 1990 and down XJ's.



Mid 23 spline input w/internal slip yoke, this came in 1991 to 1995 XJ's.



Late 23 spline input w/external slip yoke, this came in 1996 to 2001 XJ's.



242 WJ, came behind the 4.0 WJ's and can be spotted by the non machined speedo gear port on the bearing retainer housing and the non standard front output yoke.



KJ 242, came in the Liberty and is easy to spot as the bearing retainer housing has no provision for a speedo gear.



Next we move into the heavy duty versions of this case, of which there are 2ish.
First is the WJH and D 242's. These came behind V8 WJ's and Durangos, they typically sell for $300+ used. They have 32 spline input and out shafts, as well as a 1.25" wide chain. You can spot these by their long aluminum tail cone. They have no provisions for a speedometer. The only difference between the two cases is the input shaft.



Then we have the 242 AMG which is about as nice as it gets. In general this case has 32 spline input and out shafts, a 1.25" wide chain, 6 pinion planetary and an integrated cooler, no 2wd option. There are 3 versions of this case which is where the "ish" comes in.
Arguably the best option is the HMMWV 32 spline version. You can find these for $700+ usually and for around $1000 or more can find a remanufactured and sometimes brand new case. This can only be found on military Hummers and has a speedo gear provision.



Next is the 242 AMG available in the civilian H1. The only difference is there is no provision for the speedo gear, instead it utilizes a tone ring.



And last is a 242 AMG that can also be found in the military HMMWV. This only has a standard 27 spline output shaft. It can be spot with the 3 bolt tail cone, where as the 32 spline version is a 4 bolt pattern. I really have no other information about the internals of this case. Though they do still appear to have the integrated cooler.



Next we will move on to upgrade options.
For the 242 J there are finally HD SYE kits available. I say finally but they have been available for years, but I am dating myself in that back in the they did not exist. You also have the more common hack n tap kits.

Tom Wood and Advanced Adapters both offer an HD SYE kit for this case. They run about $500.



There are several hack n tap options, here is the standard Rubicon Express offering.



You can also swap in a 6 pinion planetary and a 32 spline front output. Wide chains are not an option in the J case. Unlike the NP231 the mainshaft in the HD case with the wide chain is different. The main bearing race is about .25" longer so the sprockets cannot just be swapped over.



Back to the HD case, there are no "HD" SYE kits. This may be a moot point since the output shaft is already 32 spline, but hack n tap is your only option. You have a $160 option from IRO or a $400 option from Tom Wood.

Arguably the TW kit is a better option as it is professionally machined and shortens the output quite a bit, but it does cost over twice what IRO kit runs.



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Old March 18th, 2017, 12:08
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Re: NP242 Transfer Case Tech

I am just putting this one here for posterity since there are pictures of it floating around. This is a one off SYE that Novak made. It has a billet machined bearing retainer housing and could be classified as a super short SYE. They have no plans for production.



Now lets get to what started me down this path in the first place. Swapping a 242HD case into an XJ. From a a cost standpoint the 242D from the Durango is the best candidate. It has the same 23 spline .840" input as the '91+ XJ. You could easily just swap this part over if you used a WJH case, but just one less part to worry about. Now where you run into a snag is the speedometer. The D/WJH cases have no provision for the gear. The solution to this problem is to use the bearing retainer housing from a 32 spline HMMWV case. The issue is that they are not easy to come by. You can buy them new for about $250. The second issue is the mainshaft is not machined for the snap rings that hold the blue speedo gear collar.



You can see the mainshaft on the left here does not have the retainer slots for the speedo gear.



Here are the slots in a HMMWV mainshaft.



So to put this in an XJ and have normal speedometer functionality you will need to pickup the HMMWV bearing retainer housing, have the mainshaft machined for the snap rings for the speedometer collar, and then pickup one of the SYE options if you are lifted. You can also pickup a 6 pinion planetary to swap on. All of this starts to add up and you can easily be $600+ into the case. You can basically do all of this with a replacement output shaft in a 231 for about half the cost. So you have to decide how much you want to retain full time with all of the trimmings of an HD case. You could pickup an AMG case to solve the speedo issue and then grab an SYE but you are likely near $1k at that point. Or you could stick with your J case and get an HD SYE but you are $500 for that alone, more if you want the 6 pinion planetary, 32 spline front output, and then of course there is no wide chain option.

I hope this serves to answer any questions you might have about the 242 and the options you have to upgrade it.
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Old March 18th, 2017, 12:40
jabinco jabinco is offline
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Re: NP242 Transfer Case Tech

Very interesting, thanks!
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Old March 18th, 2017, 19:41
cherokeefan_1 cherokeefan_1 is offline
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Re: NP242 Transfer Case Tech

I for sure want to keep full time and spending 1k to do it is fine if I get the wide chain and 6 pinion. Are there any other options out there besides Frankensteining one together? Aftermarket?
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Old March 18th, 2017, 19:51
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Re: NP242 Transfer Case Tech

Couple of other details.

There was a 242-J for the ZJ as well. It is very similar to the 242-J that was used with the (regular duty) WJ 4.0

All of the XJ 242s had the shift indicator switch on the rear output housing (threaded port next to the speedo) but all the other platforms used an indicator switch that was installed on the forward case half. You can see both in this pic posted above



The XJ switch uses detents on the main shift rod (see below) while the others use detents on the outside edge of the mode selector wheel. The XJ switch closes discrete circuits to activate the different bulbs, while the others use variable resistors and the computer controls an information panel. If you want the lights to work you have to use the shifter rod indicator switch.

XJ rod with indicator switch detents (not present on other models)



Mode wheel indicator detents



Front output shafts come In yoke and CV varieties. The shafts are different between them, so if you change to a yoke you will need to change the shaft as well.



There are a bunch of little obscure things about these.

should host a wiki on this stuff
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Old March 18th, 2017, 20:20
jabinco jabinco is offline
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Re: NP242 Transfer Case Tech

I have to look at mine now.

Last edited by jabinco; March 18th, 2017 at 20:24.
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Old March 18th, 2017, 20:22
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Re: NP242 Transfer Case Tech

Quote:
Originally Posted by jabinco View Post
My experience contradicts this. My 242 came out of an xj and has the switch on the forward case half, and my lights work.

Jason
Interesting. What year?
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Old March 18th, 2017, 20:25
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Re: NP242 Transfer Case Tech

Now I have to go look.
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Old March 18th, 2017, 21:03
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Re: NP242 Transfer Case Tech

Quote:
Originally Posted by cherokeefan_1 View Post
I for sure want to keep full time and spending 1k to do it is fine if I get the wide chain and 6 pinion. Are there any other options out there besides Frankensteining one together? Aftermarket?
No and if $$ is not an issue. Pickup the HMMWV 242, use XJ parts to add 2WD and get the Tom Woods hack n tap SYE. That's the easiest and best built option.
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Old March 19th, 2017, 08:21
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Re: NP242 Transfer Case Tech

Quote:
Originally Posted by ehall View Post
There was a 242-J for the ZJ as well. It is very similar to the 242-J that was used with the (regular duty) WJ 4.0
The 242 in the ZJ is the same exact case as the 96+ XJ.
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Old March 19th, 2017, 08:58
cherokeefan_1 cherokeefan_1 is offline
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Re: NP242 Transfer Case Tech

If I go with the Hummer unit is there a sye available that is not a hack job? I want the yoke supported and not just hanging off the end of the shaft.
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Old March 19th, 2017, 10:25
jabinco jabinco is offline
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Re: NP242 Transfer Case Tech

Quote:
Originally Posted by ehall View Post
Interesting. What year?
I was mistaken, it is on the tailshaft housing as you said. Apologies
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Old March 19th, 2017, 19:41
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Re: NP242 Transfer Case Tech

Quote:
Originally Posted by cherokeefan_1 View Post
If I go with the Hummer unit is there a sye available that is not a hack job? I want the yoke supported and not just hanging off the end of the shaft.
I'm not sure what you mean by supported? The yoke is splined on a hack n tap and bolts to the shaft.
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Old March 20th, 2017, 09:15
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Re: NP242 Transfer Case Tech

The "HD" 242 found in the WJs were a pretty rare bird.
They are usually found in V8s (4.7) from '02-'03 and are the 32 splined version.

The Dodge Durango and Dakota also came with the HD case, but the input is different. This can be swapped pretty easy if swapping into an XJ/MJ. Also note, the lack of speedo housing, which can be solved with a SYE.

Chrysler in all its infinite wisdom used the same engine, tranny and tcase between the WJ and Dakota/Durango, but used different adapters so the tranny outputs and tcase inputs are different.



A note on the HD 242 SYE, Tom Woods does offer one but its $750 (although, that does include a driveshaft). Per the picture it does come with a speedo housing/tail cone thing.
http://www.4xshaft.com/SYE/242HD.html

Edit: not going to include the picture, as its massive!


Correct me if Im wrong, but you could get a Dodge HD242 (32 spline outputs, 1.25" chain), swap the input for whatever you need and 6 gear planetary, and TW SYE and have a pretty robust 242.
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Last edited by Starboard M; March 20th, 2017 at 09:20.
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Old March 20th, 2017, 09:45
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Re: NP242 Transfer Case Tech

Did you read the thread? Cause that's all up there.

Quote:
Originally Posted by Starboard M View Post
Correct me if Im wrong, but you could get a Dodge HD242 (32 spline outputs, 1.25" chain), swap the input for whatever you need and 6 gear planetary, and TW SYE and have a pretty robust 242.
Only the hack n tap, the mainshaft is different between the J and HD cases. You cannot put a wide chain in a J case.
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