[TCSGTO]

Originally Posted by ID67goat

What do you guys set your pinion angle at? Just set it equal and opposite of the transmission? A few degrees down to compensate for pinion rising under acceleration? Trial and error?

Just curious, as I have been trying to get rid of a second order vibration that I get around 65-75mph.

Yes, the proper way is to set the trans tail shaft parallel to the pinion, minus a degree or so like you said to compensate for the pinion rising under acceleration. Don’t be surprised if the pinion ends up pointing upward, especially on an A-body. Fixed a pesky vibration on my car by doing it that way.
The vibration you are experiencing could also be from operating the driveshaft at 1/2 of its critical speed. There are calculators online that can give you the shafts critical speed where it becomes unstable. The only way to change that is to change the driveshafts’ diameter, wall thickness and or material.