First my dealer "road force balanced" my tires. No good. Second they installed a black box on my rear driver side leaf spring to dampen the vibration. No good. Third they installed a new driveshaft but it made it worse, they said it was defective and ordered another. No good. Finally they adjusted the angle of my driveshaft by putting a wedge under my rear springs, said it was at 3 degrees and they took it down to 1 degree. Darned if it didn't take out 95% of what i felt while maintaining between 50 and 60 mph. Hope your dealer can help yours.

 

you know someone a while back suspected that it was the angle of the driveshaft and people turned it down...good job on your service dept on finding that

 

Texsaw, please keep us posted on this with some miles on the truck, maybee this will be it!