GM-51173 contains a shim selection gauge block and two centering discs to determine the required pinion shim on 9.76"" rear axles.
GM-51173 is used with components from GM-34925 Pinion Setting Gauge Set.
The centering discs from GM-51173 hold the stud assembly from GM-34925 centered when attaching it to the gauge block from GM-51173, and allow the correct pinion bearing preload to be set.
The arbor plunger rod is placed on top of the gauge block, and moved to "zero" the dial indicator
The arbor is turned to move the rod off the gauge block, and the dial indicator reading displays the required shim.