My 780 had a bad vibration at 50mph plus, had complete front end rebuild(kingpins, bearings and a new carrier bearing, front steer tires balanced good and had retread super singles on rear. went to have them balanced and only did 2 tires on passenger side before throwing in the towel on them. one tire was 43 ounces and the other was 36 ounces (ouch) so i replaced the 4 supers with virgin tires and all the vibration is GONE, smooth sailing all the way to 85mph plus on the truck. Moma loves the ride now. hope you find the problem and enjoy the truck.