Pinion depth setting

not all 8 3/4 cases are same. i measured the case and the cap differences, using factory gears , already shows how much shim to use, after market gears have to use pinion depth . with a t & d gear setter, it measures absolute pinion depth .for years i used flat plate and measured depth, with a depth mic, if you're off on pinion depth, gears will howl like mad, just food for thought