Could it be a brake drum out of round or out of balance? I think you guys have covered all the bases with the exception of the drum itself. Seems like a long shot, but if the drum was out of round or out of balance, then it would stand to resaon that the smaller diameter of the drum would produce vibrtions or the oscillation described only at a higher speed. Too bad nobody balances wheels like they did in the old days,(On the vehicle)then you would know for sure if the vibration was wheel/tire or driveline. Too be truthful, I don't know how one would balance a drum without factory equipment. Maybe change out the drums when you do the next brake job. Good luck w/ this one, Joe
