Strange vibration under no engine load

[fiatslug87]

Hope you guys can point me in the direction to solve this issue. It's a '90, 4.0L, AX-15, 2WD. When I'm driving and lift off the accelerator, the MJ starts vibrating. Even if I throw it into neutral the vibration is there. It only happens when I'm completely off the accelerator, any load on the engine and it goes away. I don't feel it in the steering wheel (just the seat of my pants) or while not moving. All help is appreciated.

[gogmorgo]

U-joints? How does the tranny mount look?

[fiatslug87]

Tranny and engine mounts are new (had them and decided to replace after 25 years). I'll check the U-joints for play. Thanks.

[mvusse]

x2 on driveshaft u joints.

[fiatslug87]

You guys were right on the money, the front u joint was AFU. Two of the caps were dry as a bone, cracked and missing ALL their needle bearings. I bought the Harbor Freight 20 ton press for $150, made pressing them out/in a piece of cake! Thanks for the help.

[Eagle]

I bought the Harbor Freight 20 ton press for $150, ...

Massive overkill -- I've always used a bench vise. Nice to have around, though.

[Wesleypipesyo]

I always use a socket, hammer, and a couple of 4x4 blocks. But I like doing things the hard way. That's why I drive jeeps.

[fiatslug87]

Massive overkill...

Yeah, but it will also make pressing wheel bearing races a snap, among other things. Remember I have three of these beasts to keep on the road and it was only $150 with the March coupon! Plus it's another tool.