Rubbly Shuddering Thing Happening

[ajohnson928]

I'm still getting familiarized with my MJ (just got it this week) but the first (major?) thing that I think I need to fix is this vibration/rumble/shuddering.  

 

When I'm driving above 50mph and let off of the gas or shift into neutral to coast there is a significant vibration that begins.  It is a low frequency vibration that I can feel in the seat, wheel and see it vibrating an ink pen in the tray under the glove box.

 

I've done some reading on the forums but most of the time the description matches but the solution has to do with binding caused by a lift.  My MJ is factory height with 30's on stock rims, so that's not the problem.

 

I'm planning to throw some new U-Joints in it and see if that helps out any.  Does anyone else have any experience with this type of thing?

 

1989 MJ 4.0L 5spd long bed

[Eagle]

My first guess, before reaching the end of your post, was u-joints.

[coyote kid]

U joints or a possible rear end issue would be my guess

[Biotex]

Maybe a worn motor mount. When you decelerate, the weight shifts so that metal on metal happens, and transfers the vibration. Also check the tranny mount.

[HOrnbrod]

:agree: 

[ajohnson928]

For Posterity:  Got the issue fixed today.  It was the U-joints.  Specifically the rear u-joint was missing all of the needle bearings on one end.  I went ahead and replaced both ends while I had the shaft out.  Problem solved!

 

Thanks for the input.