rhythmic vibration

Get new straps and bolts for the u-joint on the rear end. They are less than 10.00 I had simular vibration that change with gearsest but never really went away. the straps helped a lot but the biggest was getting the pinion angle correct. My car was "sagging" a little and I put an extra leaf in the rear springs to get it back up and sence have not had the viberation.