- Location
- Thornton, CO
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 output 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 output 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 spotted 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 day 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.
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 output 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 output 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 spotted 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 day 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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should host a wiki on this stuff
The only way I will know for sure is to pull the DS and count splines. Mine is the 2001 limited with 242 select trac with speedo gear just like in the picture. 