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james_tessier 08-25-2011 09:15 AM

another 5.9 T-case swap
So ive been reading for about two days and im still not sure. I have a 1998 5.9, with a bad transfer case. I have a 1997 grand cherokee 4l, with a np242 i believe the select trac. Also all the driveshafts for both. I pulled the transfer case out of the 97 last night, what else do I need to put this in the 5.9. Will I need a shortened driveshaft, or what else? Theres so much to read on these subjects it gets tireing. Someone please chime in! thanks :highfive: If it makes any difference this jeep will never see off-road its strictly a grocery getter.

KingtheZJ 08-25-2011 09:59 AM

i'm assuming the 249 has an internal slip yoke (isy) and the 242 has an external slip yoke (esy).

the esy is 1.5" longer than the isy. also keep in mind the d44a has a longer pinion (i think ~1" than the d35). if you have any lift in the back you should be good with the 242 shaft, but i would definitely make sure you ont bottom out the yoke as the suspension cycles.

also, if you enter your jeeps information in your profile its easier to know what to recommend.

james_tessier 08-25-2011 10:41 AM

no lift
I dont have a lift in the back. Totally stock suspension and truck

KingtheZJ 08-25-2011 10:44 AM

what slip yokes do the transfer cases have? the isy has a tailcone that goes all the way to the end of the output shaft. the esy has an exposed shaft (can see 4" pf spline) and came with a rubber boot that attaches to the yoke.

james_tessier 08-25-2011 10:46 AM

the one on the 4.0 has a rubber boot i havent looked at the other yet

98BlackZJ 08-25-2011 11:03 AM

I did the same swap on my 98' 5.2 although mine was lifted. With the parts you have you should be able to make it work. I'm pretty sure the 5.9 uses a bigger ujoint in the rear driveshaft (1330 instead of 1310) though, so if you have to use the 4.0 driveshaft you will need a conversion ujoint. I used the longer of the two driveshafts, but at stock height you may be able to use the shorter one.

james_tessier 08-25-2011 11:08 AM

where do i get the number for the conversion u joint? also does anyone have the number for the seals handy.

CatSplat 08-25-2011 11:45 AM

Sounds like you're converting from an internal-slip 249 to an external-slip 242. There's 3 variables that determine rear drive shaft length: TC slip yoke style, rear diff model, and transmission length.

The external slip TC is about an inch or so longer than the internal variety, so the drive shaft will need to be that much shorter. Your 4.0L had the external slip TC, but also has a D35 that is an inch or so shorter than the 5.9's D44A, so that's an approximate wash. It also has the 42RE trans that is shorter than the 46RE in your 5.9, so its rear drive shaft may actually be longer than your 5.9L's.

The only way to tell for certain is to measure after you've got the 242 installed. My guess is that neither shaft will be the correct length, and the most straightforward fix would be to have the 5.9 shaft shortened, thus avoiding the conversion U-joint needed to use the 4.0 shaft.

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