my jeep is a cherokee `1989 4.0L 5 speed 4wd - after about 10 to 15 miles of driving along at 45 or more when I get a vibration that I feel in the gear shifter and then the right rear of the car shakes violently till I slow to a stop if I drive at 30 to 40 it seems fine I checked my trans mount and found 2 bolts loose , I tightened them went out for a drive and the shaking came back drive line seems good at the u joints. this happens first thing in the morning when the car is cold, this is a commuter jeep that gets driven daily 60 miles so i need to fix it if i can
I'm stuck any ideas?"

 

Sounds like one (or more) of your tires are out of balance. Probably lost a weight or two.

The first thing I would do is head to your friendly wheel shop and and ask them to balance your tires. Usually, wherever you bought them from will do it for free (you may need to ask them to rotate your tires to get the free deal).

 

What kind of shape are the U-joints in?