The Trooper has 204k miles and has developed a vibration which is felt from ~ 78 to ~ 82 mph. The vibration is primarily felt in the seat and transfer case lever more than throguh the steering wheel.

The vibration occurs at the same level in both 3rd and 4th gear so I do not believe it is an engine balance issue.

I have replaced all of the u joints and also had the driveshafts balanced. I've swapped a set of wheels and tires from another Trooper as well as having the tires on this truck balanced and rotated with no change.

My most recent attempt at resolution was to replace the front rotors and repack the front wheel bearings. The rotors felt a bit warped so I decided to just replace them at the same time. This seems to have changed the vibration in that previously the vibration occured regardless of if the truck was accelerating from 78-82mph or if it was slowing down from 82-78mph and now the vibration does not occur during deceleration.

I tried adjusting the bearings to the lightest suggested tension of ~ 3 lbs and then again to ~ 4lbs with no difference in the two settings. The bearings were not obviously bad but they do have 204k miles on them and no telling if they were ever serviced before I cleaned them up. Changing them wouldnt be expensive at under 200.00 but it is a hassle and I'm not sure where to get the proper bearing driver to install the races so I repacked them and put it back together.

I'm stumped for an explanation as to how this change could have had the impact it had (stopping the vibration on deceleration) as well as being stumped as to how to proceed on trying to fix it.

I'd sure appreciate any suggestions as to how I should proceed or even ideas as to what the problem might be.

Mark