Adjusting Differential Backlash; Tapping Final Shim Into Place; Checking Ring Gear To Pinion Backlash - Pontiac Grand Prix Service Manual

STANDARD DIFFERENTIAL
4A-25
Insert progressively larger sizes (. O lo", .0 12", .0 14",
etc.) until there is a noticeably increased drag. The
point just before additional drag begins is correct
Bauge 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 additional drag is
caused by side bearing preload. By starting with a thin
feeler gauge, a sense of 'yeel" is obtained so that the
beginning ofpreload can be recognized.
6. Remove left bearing cap and all shims from carrier.
The total shim pack needed (with no preload on side
bearings) is 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 "slip jt" of the case in the carrier. For convenience in
setting backlash and tooth contact, the preload will not
be added until thejnal 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 UTZON: If insertion of second shim causes excessive
pinion to ring gear contact (noticeable by difjculty in
rotation of the case), select thinner leJ shim and add
diffence 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 removed and
install one on each side. This additional thickness will
prbvide proper bearing preload. It will be nemsary to
tap the final shim into place with a soft hammer (Fig.
4A-48).
ADJUSTING DIFFERENTIAL BACKLASH
1. Rotate differential case several times to seat
bearings, then mount dial indicator (Fig. 4A-49). Use a
small button on indicator stem so that contact can be
made near heel end of tooth. Set dial indicator so that
stem is, as nearly as possible, in line with gear rotation
and perpendicular to tooth angle for accurate backlash
reading.
2. With pinion locked to camer, check gear lash at 3 or
4 points aroung ring gear. Lash must not vary over
.002" around ring gear. If variation is over .002",
check for burrs, uneven bolting conditions or distorted
case flange and make corrections as necessary.
3. Gear lash, at the point of minimum lash, should be
.005" to .009" for all new ears. If original gear set
having a wear pattern is
1
eing reinstalled, original
gear lash should be maintained.
4
4. If gear backlash is not within specifications, correct
by increasing thickness of one differential shim and
decreasing thickness of other shim the same amount.
In this way, correct differential bearing preload will be
maintained. Shift .002" in shim thickness for each
.001" change in backlash desired. If backlash is .001"
too much, decrease thickness of right shim .002" and
increase thickness of left shim .002". If backlash is
.002" too little, increase thickness of right shim .004"
and decrease thickness of left shim .004".
5. When backlash is. adjusted to specifications, tighten
bearing cap bolts to 70 lb. ft. torque.
Fig. 4A-48 Tapping Final Shim into Place Fig. 4A-49 Checking Ring Gear to Pinion Backlash