I have a 1989 auto with the 242 tcase. When i get to 30 mph, the whole jeep vibrates like crazy. Its only when im on the gas though, it feels fine while coasting. The really wierd (to me) thing is when it is in 4 wheel drive it goes away completely. When i realized it went away in 4wd, i just drove it home in 4wd full time, and it was totally fine. The jeep is lifted, bit it hasnt done it before. I have checked the u joints for play, but they seem fine. I have a sneaking suspicion that the problem lies in the tcase, but idk. Any help would be greatly appreciated.

 

I'd bet it's a U-Joint. I'd pull the drive-line and have a good look before I'd drive around in 4WD. Sounds like maybe 4 wheel is binding the play out of it. (like, the front is pulling the rear).

 

Mines doing the exact opposite, in 4wd it'll kinda shudder/chatter. But in 2wd it's smooth. Also a NP242J t case, although in a 99 XJ sport.

 

same here, im just gettin a "new" tcase screw it

 

What should i look for when i take it off? From what i can see, the u joints look fairly new.

 

Feel for roughness rotating/twisting the yoke & caps. You'll be able to remove two caps on the rear. Should be completely smooth and tight. While your there jiggle the pinyon yoke on the diff. Mine has a little "clearance" but so far so good! (my ****ing bottle just blew! It's sitting out in the driveway "taking a leak" )

 

I know how you feel, mines in the garage cause it started pissin blood out of one of the tranny lines that i need to fix too.