I had a vibration problem , Thought it was a wheel bearing since it felt like it was first coming from one wheel . I found out it was my UJOINT Mount that goes into the Rear Transfer Case(Rear Driveshaft). The mount was slightly bent and my mechanic tried to BANG IT back into shape BUT I had to order a new one and once I Did that and replace the ujoints it was ALL GOOD and havent HAD ANY PROBLEMS. If I were you guys I would go to a DRIVELINE/DRIVESHAFT Expert and have them check out the whole thing. IF any piece is slightly bent (even a hair) it throws the whole drive shaft off,since its balanced,and it feels like the truck is shaking or you have bad wheel bearing(s).
AND by the way dont take it to the dealership those guys dont know DIDLY SQUAT. They turned my rotors ,replaced tha brake pads,check the wheel bearings and had the shop foreman test drive my truck and they couldnt figure out the problem.
JUst saying if you've checked the obvious out Brakes and bearings. this will be the next logical area to go to next. Especially if you have lifts and can put a strain over time on the drive shafts