GMC 1982 Light Duty Truck Service Manual page 442

4 B 1 - 1 4 REAR A X L E
"ZERO" THE INDICATOR,
WITH THE PROBE ON
THE HIGH POINT OF
THE GAUGING SURFACE.
SWING THE PROBE OFF
THE GAUGE PLATE.
THE INDICATOR NEEDLE
WILL MOVE TOWARD. . . .
THE PROPER NUMBER,
WHICH INDICATES THE
REQUIRED SHIM FOR A
NOMINAL PINION.
THIS NUMBER IS THE
CORRECT SHIM THICKNESS
FOR A NOMINAL PINION.
V
Fig. 4Bl-37--Use of Dial Indicator