I had a cyclical vibration above 65 MPH in my ’67 for years. I changed wheels and tires, had the driveshaft balanced, and even replaced the driveshaft but never managed to get rid of the vibration. Nothing I tried got rid of the annoying vibration until last week.
The other day I was at Harbor Freight and picked up a cheap angle finder. When I checked the pinion on the rear end I found it was pointing down 4º. The transmission was also pointing down 3½º. From everything I have read about proper driveline setup these numbers were way off. The way I understand it the transmission and the rear end should be parallel to each other for the U-joints to operate smooth.
In other words with my transmission pointing down -3½º, the pinion on the rear end should have been pointing up +3½º not down -4º. My pinion angle was way off.
I ordered some 4º leaf spring shims to correct the pinion angle. I actually used two 4º shims on each side. I placed one shim on top of the spring and one facing the other way on the bottom so the shock plate would sit level. I also eliminated the rubber spring pads in the spring perches. I had to add a 3/8 inch thick spacer and a longer bolt to the spring pack so it would fit tight in the perch.
I also made a ½ inch spacer for under the transmission mount to raise the rear of the transmission. My transmission is now 2º down and the pinion is level or 0º. The leaf springs should wrap up a couple of degrees from the axle torque which will hopefully put the pinion 2º up while running down the road.
It’s now smooth as glass.
I am convinced Chevrolet Engineering simply screwed up when they came up with the out-of-phase driveshaft and the incorrect pinion angles in first generation Camaros. I wonder how many first gen Camaros are out there with a high speed driveshaft vibration from an incorect pinion angle.