Pontiac tempest 1968 Service Manual page 145

4A-22
1968 P O N T I A C SERVICE MANUAL
F i g . 4A-42 Installing Two Service Shims
Insert progressively larger sizes (.010", .012",
.014", etc.) until there is a noticeably increased
drag. The point just before additional drag begins
is correct gauge thickness. Rotate case while using
gauge to insure an even reading.
NOTE: The original light drag was caused by
weight of the case against the carrier while addi­
tional drag is caused by side bearing preload. By
starting with a thin feeler gauge, a sense of "feel"
is obtained so that the beginning of preload can be
recognized.
6. Remove left bearing cap and all shims from
carrier. The total shim pack needed (with no preload
on side bearings) i s feeler gauge reading found in
step 5 plus thickness of shims installed in step 4.
NOTE: The object of step 6 is to reach the
equivalent of a (i slip fit" of the case in the car­
rier. For convenience in setting backlash and tooth
contact, the preload will not be added until the
final step.
7. Select two shims of approximately equal size,
whose total thickness is equal to the value obtained
in step 6. Install one of these shims between each
side bearing race and service spacer.
CA UTION: If insertion of second shim causes
excessive pinion to ring gear contact (noticeable
by difficulty in rotation of the case), select thinner
left shim and add difference to the right side.
Keep total shim thickness at a value equal to that
obtained in step 6.
8. Check backlash and tooth pattern as described
in the following section. The bearing caps must be
installed and the bolts torqued to 70 lb. ft.
9. When backlash and tooth pattern operations are
complete, remove shim pack installed in step 7.
Select two shims each .004" thicker than those r e ­
moved and install one on each side. This additional
thickness will provide proper bearing preload. It
will be necessary to tap the final shim into place
with a soft hammer (Fig. 4A-44).
ADJUSTING D I F F E R E N T I A L BACKLASH
1. Rotate differential case several times to seat
bearings, then mount dial indicator (Fig. 4A-45).
Use a small button on indicator stem so that contact
can be made near heel end of tooth. Set dial indica­
tor so that stem i s , as nearly as possible, in line
with gear rotation and perpendicular to tooth angle
for accurate backlash reading.
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F i g . 4A-43 Inserting Feeler Gauge
Fig. 4A-44 Tapping Final Shim into Place