Drivetrain vibration at high speeds....only when decelerating?

[BKSRR]

It's my Cuda (not my RR) runs well at highway speeds BUT at high speeds there is a terrible vibration felt in the shifter as you let off the gas. I balanced the tires and that might have helped a little....is balancing the driveshaft next?? Replace the U-joints???
Thanks!
BK

 

[Russ69Runner]

Might be U-joints need replacing.

 

[BKSRR]

That's my next "try"..... thanks for your reply!