np242 drive shaft help needed.

[DatGuyC]

I'm going to be swapping a np242 transfer case into my hmmwv when I do the cummins conversion. Right now the truck is a 93 m998 with a 218. I've been looking online and it seems there are a few different rear drive shafts that work with the 242 and I don't know which one I need. I think I have a later version of the 242 since it has 4 tabs on the output housing where it bolts to the transfer case, and I think the later versions are supposed to have a thicker output shaft. I'm not sure so would like some help from someone who has done this conversion and knows which shaft I need.

 

[Dock Rocker]

If I were you I would build it out and get the motor, trans and transfer case mounted and then just have custom drive shafts cut so they will fit exactly as they are supposed to.

I have done that with several different motor conversions over the years and it has saved quite a bit of headache and parts matching. It will allow you to run heavier more durable U-joints as well.

 

[DatGuyC]

With the length of the cummins and the 47rh I'm going to need the driveshafts resized anyways, but I need the slip yoke part that goes into the 242 from the rear since its completely different from the 218. I'm not sure if a jeep np242 driveshaft would be the same as the np242 the hummer has.

 

[Retiredwarhorses]

It just depends on if you have the new style or old style 242. Post a pic of the tail shaft. The older is a 3 bolt, the new is 4 bolts. The spline count is different on both. Once you find the tcase type..getting the PN is easy.
I have both in the shop, the old one is slimmer on the slip yoke side, the new is beefier...

 

[DatGuyC]

Picture of the rear area when I had it apart and was inspecting it. It has the 4 bolts so it should be the later type. Also a picture of the tag, I think it was made in 03? I know it has the upgraded cooling loop.

 

[Retiredwarhorses]

Yes, later model.....so you need the fatty. They are a little more expensive then the early model.

 

[Retiredwarhorses]

12469284

 

[DatGuyC]

Ok thanks a lot. I think I was also reading somewhere that the u joint size is different for the 12k differentials and the 7k ones I have. Is this true?

Edit: After some digging the stock drive shaft I have now should be using 1330 ujoints. The 12k drive shaft takes 1350 ujoints. They make 1330 to 1350 conversion ujoints so using one of those should make everything fit properly I think. More specifically a Spicer 5-648x.

 

[Retiredwarhorses]

Just change out the yoke on the diff....they are plentiful. I would not go smaller u-joint.

 

[DatGuyC]

Alright, that seems to be part #3-4-11901-1 for the 12k version. I've never done a pinion before, is it just a straight swap or am I going to have to re-adjust the internals of the differential?

Also for the front drive shaft I think I need a new back half that uses 1330 ujoints for the tcase side , nsn 2520013575043? Dang, figuring out what goes with what is a pain in the butt haha.

 

[Retiredwarhorses]

Alright, that seems to be part #3-4-11901-1 for the 12k version. I've never done a pinion before, is it just a straight swap or am I going to have to re-adjust the internals of the differential?

Also for the front drive shaft I think I need a new back half that uses 1330 ujoints for the tcase side , nsn 2520013575043? Dang, figuring out what goes with what is a pain in the butt haha.

yep...gonna need that too. Its the same as if you were going 4L80E and 242, the front yoke is larger for the 242.
if you stick with the 1330 's for the front diff, you can keep the front/front drive shaft with carrier bearing.
when you go with the larger front pinion, the carrier shaft changes to a shorter or longer, can't remember...you would think as many as I have done and do I would know, but when I go to mount them, if the carrier bearing don't line up with the frame mount, I go grad the other one in my stash. The 2 part number are 12342620 and 12342620-1 for the shafts, the 2620 is the 218, the -1 is the larger and longer, or shorter...can't remember.

 

[Retiredwarhorses]

Look in the TM the part might be a 2520012003096

it lists 3 shafts based on Tcase. You have to look at the UOC "use on code" to see which truck applies.
when I order, I just tell them what I have...I let my parts guy do the leg work.
but I have done older small front yokes on 256 diffs with 242's and had to use the shafts supplied in the
242 MWO.

 

[NormB]

I'm going to be swapping a np242 transfer case into my hmmwv when I do the cummins conversion. Right now the truck is a 93 m998 with a 218. I've been looking online and it seems there are a few different rear drive shafts that work with the 242 and I don't know which one I need. I think I have a later version of the 242 since it has 4 tabs on the output housing where it bolts to the transfer case, and I think the later versions are supposed to have a thicker output shaft. I'm not sure so would like some help from someone who has done this conversion and knows which shaft I need.

Hate to resurrect an old post, but I'm doing this same thing, just picked up the 242 this morning up in Philly.

I'm at a loss to tell which shafts I'll need.

Did you ever sort this out?

Norm (just down the street from you).

 

[86humv]

3 or 4 bolt tail shaft housing ?

 

[NormB]

3 or 4 bolt tail shaft housing ?

4, definitely 4. On cone and on case.

NB

 

[86humv]

Is your rear yoke like one of these :


And...is your front diff yoke like one of these :

 

[NormB]

It looks like this:

 

[DatGuyC]

I never got it strait because there are so many different applications. They have the early/late style 242 and it is either paired with the three speed or four speed with the 4 speed being a little longer so that affects the length. I ordered a 12447113 which fits the later 242 and has a 1330 ujoint on the diff side so I think that might be what you're looking for. I also got a 12342618 for the front but I haven't tested that on anything.

 

[NormB]

This is such a common topic - and I've searched this forum, hummerknowledgebase, G503, "the innerwebs" - you'd think there would be doctrine, a TB or MWO somewhere, or at the very least a table with transmission, T/C and matching shafts , one from column A, one from column B, plug and play.

Or is that hopelessly naive?

I managed my unit's ARs, TMs and pubs for a couple years in Germany, the picayune detail amazed me.

Anyone have a suggestion on how to go about this logically, withotu having to "grab one off the shelf" and check what fits what?

I don't have a shelf like that.
.

 

[DatGuyC]

From looking back at the TM I think this should be right:

5937387 AND 12342643-1(early 242)
12447125(late 242)
2520013575044 rear shaft for early 242 with 3 speed
2520014590050 rear shaft for late 242 with 3 speed
2520014132724 rear shaft for late 242 with 4 speed
2520014240425 rear shaft for late 242 with 4 speed and 1350 rear diff ujoint
2520013575043 rear part of front shaft for both 242 with 3 speed
2520014130080 rear part of front shaft for both 242 with 4 speed