Vibration

Hey guys, hope you all can give me some advice on this. I'm experiencing a vibration from 55-60 MPH. Not real severe, just annoying. Under and over this speed it's smooth. Feels like it's not in the steering wheel, more like a seat of the pants thing. Had the wheels balanced twice, even watched them, all wheels are smooth up to 80 MPH. Replaced both u-joints too, no help. Driveshaft is not scarred or dented. What's next, tranny or engine mounts? This is aggravating, I like a smooth ride. Thanks; Don

2WD 91 MJ Long Box, 4.0L w. A/T
Stock, No Lift
104K Miles

If this is a before/after thing-as in, it wasent doing this before/now it is-
my first guess would be the u-joints being out of phase. Just for kicks, switch your tires front to back.

Pinion bearing?

Front axle u-joints?

Front hub bearing?

2WD, long box MJ. Had a few replies that other owners of long bed MJ's have had driveshaft balance problems, guess this is the next most logical step in the elimination process. After that, tranny and engine mounts in that order. Annoying as hell. Thanks for the replies all.