[1966shortwide]

Have you ever jacked up rear suspension and check for bent axle"s.put jack stand"s under differential and let engine idle in gear and see if drum"s run straight and axle"s and wheel"s also.if you don"t see anything run the engine at a faster speed up to about where you noticed the vibration when driving on the road, and see if you feel any vibration .Be sure you have a jack stand under each side of differential when you do this.