I have a 1934 chevy 1 1/2 ton long wheelbase. I am trying to find what causes a vibration when I'm in 4th gear and going over 30 miles an hour. It doesn't occur all the time. If I let off the gas and step on it sometimes it will go away. I have the propeller shaft off and the tranny open though the PTO opening. Inside the trans look fine an feels tight. The ujoints don't seem to have any play. I did find wear on the front propeller shaft and bushing. It looks to be a little less that 1/16th of an inch of wear. Would this let the ujoint behind the trans slide off center enough to create this vibration? Does anyone know of any other possible sources of a vibration like this?