I don't like to shim up a tranny. If the tranny binds against the floor or anything, IT WILL VIBRATE THE WHOLE BODY. Just adjust the metco arms to set the angles. Example: If the tranny is -2 (down), and the pinion is +2 (upward), you will have parallel lines. If you jack the car up at the rear axle 2 degrees, you could now get readings of O and O. Imagine if you drew a line through the pinion shaft toward the transmition. That line would run just above the trans output shaft. A line from the tranny shaft would continue just under the center line of the pinion and these lines would be parallel to each other and very close together. The angles you get depend on how the car is setting so you only compaire the LINES to determine pinion angle or it's relation to the trans. To acheave a -2 negative pinion angle on the first example, the pinion needs to be adjusted downward from +2 to 0 degrees. Second example= from O degrees to -2 (down). My 67 GS was -4 tranny and -3 pinion which is -7. I adjusted my pinion up 5 degrees for a -2 pinion-trans difference for racing. If I had jacked up my rear axle until the trans was LEVEL (O degrees) my pinion would have been -7 down, and after adjusting, it would be -2 down from the tranny's level 0 line. Hope this makes sense.
the was I did it was-drove it up on ramps, measured the height to bottom of front wheels, jacked the rear end up at the diff to the same height so the car was level to the ground. measured the angle on the pan then measured the angle on the drive shaft-the diff was -2.(tranny-0, shaft- -2). so I need to set the rear 0 to 0 to get -2 total? man I sucked in geometry.
Don't worry about the DRIVESHAFT angles on an A Body GM. . Just set the pinion at the rear and the tranny at the front. The driveshaft will take care of it's self.
