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48-20
1977 PONTIAC SERVICE MANUAL
Fig. 48-43 Installing Differential Adjusting Shims
Install side bearing caps, as previously marked, and
tighten bolts to 55 Ib.ft. before checking side bearing pre-load
or backlash.
3. Rotate differential case assembly several complete
turns to seat bearings. Check bearing pre-load, using an inch
pound torque wrench connected at pinion nut.
Bearing pre-load should read 35-40 1b.in. of rotating
torque with new bearings or 20-25 Ib.in. of rotating torque
with reused bearings. If pre-load is not according to these
specifications, increase shim thickness on each side .002" for
each additional 10 Ib. in. pre-load desired, or decrease shim
thickness ,002" on each side for each 10 Ib. in. pre-load to
be subtracted.
ADJUST DIFFERENTIAL BACKLASH
1. Rotate differential case several times to seat bearings,
then mount dial indicator as shown in Fig. 4B-44. 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 carrier, check gear lash at 3 or
4 points around ring gear. Lash must not vary over .001"
around ring gear. If variation is over .001", 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
,006" to ,0013" for all new gears. If adjustment is necessary,
adjust to .007".
If original gear set having a wear pattern is being
reinstalled, original gear lash should be maintained within
plus or minus . O O 1 ".
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 pre-load will be maintained.
Shift ,002" in shim thickness for each .001" change in
backlash desired. If backlash is .002" too much, decrease
thickness of right shim .004" and increase thickness of left
shim .004". If backlash is .002" too little, increase thickness
of right shim .004" and decrease thickness of left shim .004".
Fig. 48-44 Checking Ring Gear to Pinion Backlash
5. Install new cover, gasket and cover torquing bolts to
30 Ib.ft.
After waiting 20 minutes, retorque bolts to 30 Ib.ft.
INSTALL AXLE SHAFT ASSEMBLIES
1. Apply a coat of wheel bearing grease in bearing
recesses of housing.
2. On Non "C" Lock type axles, apply gear lubricant to
the splines at the inner end of the axle shaft. Carefully install
axle shaft assemblies until splines engage in differential to
avoid damage to seals.
3. For "C" Lock type axles, proceed as follows:
a. Add a small amount of grease between seal lips and
insert axle shaft through the seal and bearing and, as far as
possible, through the side gear. D o not drag shaft across seal
lip.
b. InstaIl "C" lock onto axle shaft. Move axle shaft and
"C" lock outward to bottom the "C" lock in the recess of the
side gear.
c. Install pinion shaft and secure with lock bolt (15
1b.ft.).
d. Install new gasket and cover, torque bolts to 30 Ib.ft.
e. After 20 minutes, retorque bolts to 30 Ib.ft.
f. Install specified quantity and type of lubricant.
CAUTION: Fasteners in steps 4 and 6 are
important attaching parts in that they could affect
the performance o f vital components and systerrs,
and/or could result in major repair expense. These
must be replaced with one o f the same part number
or with an equivalent part if replacement becomes
necessary. Do not use a replacement part o f lesser
quality or substitute design. Torque values must be
used as specified during reassembly to assure
proper retention o f these parts.
4. Place retainer over studs and install nuts. Tighten to
specified torque.
5. Install brake drums over wheel bolts.
6. Install wheels and tighten wheel nuts to specified
torque.
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