Any ideas on why I am getting a high speed drive line vibration when I let off the throttle at speeds over 70mph on my 66 442. U-joints are good and properly installed. I tried changing the orientation of the driveshaft with the rear end with no change. There is no vibration when accelerating or cruising, just when I let off at higher speeds and no difference if I push the clutch in or shift to neutral. Thanks Jim.

 

driveline angle change on decel. Could have a bad trans mount, rear control arm bushing for your rear. I would start looking at this since you don't have it on accel or steady state.

 

On my G body I had vibration .I took it to a driveline shop and they rebalanced the driveshaft. Fixed .

 

Had a vibration in my '65, found the driveshaft to be too straight. Added couple washers under trans mount bolts to add a bit of an angle.

 

Thanks guys, sounds like I need to take a good look at the condition of my rear end bushings and trans mount.