65 Valiant Vibration /6 and 904

[Jeff Lemon]

At 55 MPH and above I have a vibration in the front seats and floor but not in the dash or steering wheel. Tires are new and balanced correctly. Prior to me owning this car the ball and trunion was removed and later driveshaft was installed. U joints and transmission mount seems find. Can anyone help?

Thanks, Jeff

 

[RedFish]

When I suspect a U joint problem I proceed to replace them. Odds are I'll see the problem when I get them apart.
On the other hand.. My similar vibration at speeds above 65 is coming from 2 bent wheels. Lots of weights on those 2 is the visual evidence. Spin balancing isn't a cure.