GMC 1990 Light Truck Repair Manual page 262

4C2-10 9 /4-INCH RING GEAR FRONT AXLE
3
• This reading indicates the amount of shims
needed for a nominal pinion setting. The
pinion marking may change the pinion depth
by adding or deleting shims from the nominal
pinion setting.
• A positive ( + ) pinion marking indicates that the
distance between the ring gear centerline and the
pinion head must increase by the number of
thousandths marked on the pinion. This means that
the shim pack will decrease by the same number of
thousandths.
• A negative (-) pinion marking indicates that the
distance between the ring gear centerline and the
pinion head must decrease by the number of
thousandths marked on the pinion. This means that
the shim pack will increase by the same number of
thousandths.
• A pinion etched zero (0) will use the nominal setting
as determined in this procedure.
Figure 27—Scooter Gage on the Arbor