Quote Originally Posted by firebird77clone View Post
Ok I did some digging. It looks like the 3* is not a fixed angle. It depends on the suspension. Ladder bars being most rigid, require 1* down. Four bar 1.5*. Leaf can be as high as 7* down. This is to compensate for the tendency of the pinion to rise under hard acceleration, maintaining the overall pinion angle at zero or less.

It is nasty mojo for the pinion angle to become positive.

Relative to transmission of course.

I hope I regurgitated that correctly.
All of which applies to a car/truck in a RACE setup, NOT a street application. For a street application the pinion angle should be equal and opposite to the transmission tailshaft angle, to eliminate driveline vibrations, IMHO.