No, what would you be referencing the angle to? The pinion is set from 2 to 4 degrees down from the centerline of the crankshaft/output shaft centerline. CenTex is correct in stating the angle is best set when the normal weight is on the truck. Two things occur when the angle is correct, when accelerating the pinion rises and pushes the front yoke deeper onto the splines until zero degrees is reached then starts to draw it back out as it goes above zero degrees and, anything off of zero degrees rotates the U-joint in the bearing cups thus preventing flat spots on the needle bearings.

Evan