Help please! Need NP242 transfer case specs

[amarshall]

I'm working on a 1988 Eagle Wagon project (build thread is in the project car section) and it's almost time to upgrade the transfer case.  I'm wanting to add a low range, and I've decided to go with a NP242.  There are several versions of the NP242, and I just can't seem to get all the details clear in my head.  If anybody can help, it would be much appreciated!

My wagon has the 258 with the 998 auto transmission.  I know I need a 23 spline input shaft, and that I want an earlier case that still has a speedo cable connection on the case.  Later versions (found in WJ's) look like they got rid of the speedo cable hole.

The big question is what input shaft length do I need?  Apparently the Jeep Cherokee XJ's had several lengths of input shafts (appropriately named long, short, and very rarely medium).  Several posts here on the board hint that the Eagle would need the long input shaft version, but I can't find it said plainly anywhere.

I  know this has been covered before, but believe me I've read it and can't find a clear answer.  If there's a source I've missed, please shoot me a link and I'll give myself a dope slap!  I'm really hoping to get this figured out and upgraded int he next few weeks.

Thanks for any help!

[eaglefreek]

I was never able to find that info myself, when I was looking a few years ago. I assume it's whether it came behind an auto or manual transmission. But I don't know which one is which.

[amarshall]

Well, at least I know I didn't miss something easy then!  I guess the only real way to get it right is to take out my current case and measure, before going shopping.

[eaglefreek]

Did you see this chart? I don't know how I missed it. https://www.novak-adapt.com/knowledge/np-nvg-input-gears/  I know this pertains to the 231, but it should be the same for the 242. It looks like you'll only find a short or medium shaft 242 because I don't think they came behind a NV3550 or a NSG370 since those were TJ transmissions and only came with NP231's. Like I said in an earlier post, my buddy Paul has had a  242 behind a 727 for 15+ years. He just had to plug the hole in the transfer case adapter because now the adapter is filled with fluid from the transmission. I don't know how much of an issue with the almost one inch less of spline engagement will cause.

[eaglefreek]

Ok, I did a little more digging. Did you see this? https://kevinsoffroad.com/249-to-242-swap-instruction-guide/ Apparently, if you can find an input shaft from a V8 Grand Cherokee's NV249, you can swap it for the 242's input shaft.

[amarshall]

Did you see this chart? I don't know how I missed it. https://www.novak-adapt.com/knowledge/np-nvg-input-gears/  I know this pertains to the 231, but it should be the same for the 242. It looks like you'll only find a short or medium shaft 242 because I don't think they came behind a NV3550 or a NSG370 since those were TJ transmissions and only came with NP231's. Like I said in an earlier post, my buddy Paul has had a  242 behind a 727 for 15+ years. He just had to plug the hole in the transfer case adapter because now the adapter is filled with fluid from the transmission. I don't know how much of an issue with the almost one inch less of spline engagement will cause.

I had seen the Novak page, but every time I read it I come away with new info.  Today it is telling me a 242 from a Cherokee XJ with AW4 will probably be a medium length input shaft.  I wonder why Novak calls the medium length "rare" when the vast majority of XJ's were automatics and so this should be a pretty common thing??

Ok, I did a little more digging. Did you see this? https://kevinsoffroad.com/249-to-242-swap-instruction-guide/ Apparently, if you can find an input shaft from a V8 Grand Cherokee's NV249, you can swap it for the 242's input shaft.

Thanks! I had not seen this one, I will study it.  Are you saying the V8 Grand Cherokee 249 shaft is known to work with the Eagle and 998?

Hmmm. Since we are talking about changing input shafts, could I take the shaft out of my 129 and put it into a 242?

[eaglefreek]

Just assuming since the Grand Cherokee has a long shaft. Heck, all 249 GC transfer cases might be the same since they used a Chrysler transmission. No idea about the differences between the 129 and 242 input shafts.

[mudkicker715]

When i swapped in my 242 i only had to do the rear driveshaft lengthening. The front drive shaft was able to squish together to work. I mean since its all bolted to the motor it works.the front drive shaft almost needs no slipshaht. My 242 came froma 94 xj.

[amarshall]

I am planning to take out the existing case first before dropping cash on a 242. I've found several listed in junk yards near me but want to be sure they will fit. Best guess at this point is that the medium length input shaft will work.

Makes sense about the front shaft, it really can't move very much. For the rear shaft, I saw some old posts (won't say from who) about using a 3" section of pipe to disable the existing slip joint in the shaft. What do you guys think of that? I know it's sketchy, but is it unsafe?

[mudkicker715]

Yup i remember that being posted. My opinion on that is not to do it. That slip shaft is there for a reason. Even if it makes no sense to be there.

[amarshall]

Whoops, I forgot to mention the rest of the story. The idea was to use a slip yoke from the 242 donor vehicle and put in front of the Eagle rear shaft. This lengthens the rear yoke so the shorter Eagle driveshaft will connect. But now there would be two slip joints and if both move at the same time the driveshaft could drop out. So the idea was to disable the slip joint in the driveshaft with some pipe and rely only on the slip yoke behind the 242.

I'm still not 100% on this idea, for safety reasons.

[eaglefreek]

Personally, I would just have a new driveshaft made. Being in South Florida, it should be easy to find 2wd Jeep Cherokee rear driveshaft which will need to be shortened. Shortening an old shaft doesn't cost as much as having new shaft made.

[amcfool1]

or, just buy a Jeep!:)

[amarshall]

Hah, my daily driver is a 2000 Jeep Wrangler.  I'm having much more fun working on the Eagle though!