Hi all,

Thanks a lot for all the responses, and sorry for taking so long for this update. My friend finally got the car to a driveline shop to have everything checked out. The U-joints were fine, but both ends of the drive shaft were slightly out of balance. The shop straightened and re-balanced the shaft, and the situation has improved quite a bit. Now, in 3rd gear @ 5,500 rpm, under load at 100 mph, there is no more vibration. However, there is still a slight vibration in 4th gear @ 4,500 rpm, under load at 100 mph. His angle at the rear of the transmission is 4-5 degrees, so the shop thinks there may still be some binding at that joint.

Special thanks to CKessel for the reference to this Hot Rod article. My friend really likes the idea of a front CV joint, on an aluminum drive shaft. He will likely look into that.

Moparts to the rescue again!

Roger