GMC 1990 Light Truck Repair Manual page 166

4B3-6 91 / 2-INCH RING GEAR
12. Set the dial indicator at zero. Push the indicator
down on the indicator shaft until the needle rotates
approximately 3 U of a turn to the right. Tighten the
dial indicator in this postion (figure 13).
13. Rotate the gage shaft slowly back and forth until the
dial indicator reads the greatest deflection (when the
indicator needle is centered between movement to
the left and to the right).
14. At the point of greatest deflection, set the dial
indicator to zero. Repeat the rocking action of the
gage shaft to verify the zero setting.
A. Dial indicator and arbor positioned on the gage block.
B. Measurement after the arbor is moved o ff of the gage block, j A
15. Rotate the gage shaft until the dial indicator rod
does not touch the gage block.
16. Record the actual number on the dial indicator and
not the number which represents how far the needle
travels. This is the nominal pinion setting.
EXAMPLE: If the indicator needle moved to the left
1.70 mm (0.067-inch) to a dial reading of 0.84 mm
(0.033-inch) as shown in figure 13, record the dial
reading of 0.84 mm (0.033-inch) not 1.70 mm
(0.067-inch).
17. Check the pinion face for a pinion adjustment mark.
This mark indicates the best running position for the
pinion from the nominal setting.
18. Remove bearing caps (10) and depth gaging tools.
19. Install the correct pinion shim (6) to the pinion
according to this procedure.
Figure 13—Checking Pinion Depth
• If the pinion is stamped with a plus number,
add that many thousandths to the nominal
setting. If the nominal setting is 0.033-inch and
the pinion is marked +2, the correct shim
depth would be 0.033-inch + 0.002-inch =
0.035-inch.
• If the pinion is stamped with a minus number,
subtract that many thousandths from the
nominal setting. If the nominal setting is
0.033-inch and the pinion is marked -2, the
correct shim depth would be 0.033-inch -
0.002-inch = 0.031-inch.
• If the pinion has no plus or minus marked on
the pinion, use the nominal pinion setting to
select a shim.
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F-04682