Is there any way to tell difference between pinion angle or driveshaft vibration. It gradually gets worse the faster you go.I will recheck pinion angle but thought I had it right.

I would guess driveshaft out of balance.

Do you have an overdrive transmission and have you changed the gears in the rear end? At what speed do you have the vibration?

Transmission is a th400,gears have been changed but vibration was there before that. Went from 4.56 up to 4.11, had to work today but will try and check angle tomorrow.

Run it on jack stands watch for trueness if true get it balanced also wtch for mis installed/ misaligned ujoint at both ends...c

I rebuilt an 8.5 inch 10 bolt with a posi a couple of years ago. I had a vibration that was so bad at 65-70 that I thought the car was coming apart. I found that the pinion angle was incorrect, bought adjustable upper control arms and corrected it, but the vibration was still there.

I looked at everything I could x3 and finally noticed that my yoke was stretched out. The cups would move a very small amount with everything tight......I could not believe how it was stretched once I noticed. I got a new pinion yoke and no more vibration. Amazing how not turning the driveshaft into a rotating hammer helps quiet things down.

Check your bearings too...they can cause vibration..
The ones in the back of the tranny, the ones on the pinion and the ones in the Ujoint.
Ron