engine PONTIAC FIERO 1988 Service Service Manual

3E-8 TIRES AND WHEELS
nearest the valve stem, and a 1/2 ounce balance weight
should be added 180" opposite the locking nut on the
wheel's inboard side.
When rotating tires, always re-install the locking
nut nearest the tire valve stem so that it remains
opposite the 1/2 ounce balance weight. This procedure
will improve the on-car wheel balance by compensating
for the heavy locking wheel nut.
Off-Car Balancing
Most electronic off-car balancers are more
accurate than the on-car spin balancers. They are easy
to use and give a dynamic (two plane) balance.
Although they do not correct for drum or rotor
unbalance as does on-car spin balancing, this is
overcome by their accuracy (usually to within 1/8
ounce). When balancing off-car, the wheel should
locate on the balancer with a cone through the back
side of the center pilot hole (not by the wheel stud
holes).
On-Car Balancing
When needed, on-car balancing will help correct
vibrations due to brake drum, rotor, and wheel cover
imbalance.
When balancing on car, do not remove the
balance weights from the off-car dynamic balance. If
more than one ounce of additional weight is required,
it should be split between the inner and outer rim
flange.
NOTICE: The driven tire and wheel assemblies
should be spun using the engine. Limit speed as
stated in the following Caution.
CAUTION: Do not spin the drive
wheels faster than
35 mph (55 km/h)
as indicated by the speedometer. This
limit is necessary because the
speedometer indicates only one-half
of the actual wheel speed when one
drive wheel is spinning and the other
drive wheel is stopped. Personal injury
and damage may result from high
speed spinning.
CAUTION: On cars equipped with
limited slip rear axles, do not attempt
to balance a tire on a
drive wheel with
the other drive wheel on the ground.
The car may drive through this wheel
and cause the car to move
unexpectedly, resulting in personal
injury and property damage.
To distinguish between standard rear axle and
limited slip, raise rear of car so both tires are clear of
ground. With the transmission in park (in gear with
manual transmission), attempt to turn one wheel by
hand. If the wheel can be turned, it is a standard rear
axle; if the wheel cannot be turned, it is a limited slip
rear axle. Also, check for Limited Slip
(G80) on Service
Parts Identification label.
Wheel Weights
Fig. 15
If more than 27 grams (1.0 oz.) are needed, the
wheel weights should be split as equal as possible
between the inboard and outboard flanges.
Balancing of' assemblies with factory aluminum
wheels requires the use of special nylon coated clip-on
type wheel weights. These weights are designed to fit
over the thicker rim flange of the aluminum wheel and
should be installed with a plastic tipped hammer.
Adhesive wheel weights are also available. Use
the following procedure to install adhesive wheel
weights.
Adhesive Wheel Weight Installation
1. Clean wheel by sanding to bare aluminum where
wheel weight is to be located.
2. Wipe wheel weight attachment area with a
mixture of half Isopropyl alcohol and half water.
A clean cloth or paper towel niust be used for this
operat ion.
3. Dry the attachment area with hot air. Surface of
wheel should be warm to the touch.
4. The adhesive backing on wheel weights must be
warmed to room temperature.
5. Remove tape from back of weights. Do not touch
the adhesive surface.
6. Apply wheel weight and press on with hand
pressure.
7. Secure wheel weight with a 70-1 10
N (16-25 lb)
force applied with a roller.
CENTERLINE
1 INSIDE FLANGE CLIPBN WEIGHT 4. ADHESIVE WEIGHT - DYNAMIC 5. ADHESIVE WEIGHT -STATIC ONLY 6. MOUNTING FACE
Fig. 15 Aluminum Wheel Weight Placement
CORRECTING NON-UNIFORM TIRES
There are two ways to correct tires which cause
a vibration even though they are properly balanced.
One method uses an automatic machine which loads
the tire and buffs small amounts of rubber from high
spots on the outer two tread rows. Correction by this
method is usually permanent and, if done properly,
does not significantly affect the appearance or tire
tread life. Tire truing with a blade-type
machine is not
recommended as this reduces the tread life
substantially and often does not permanently correct
the problem.

3E-10 TIRES AND WHEELS
Clear Coat Damage on Unpainted Wheels
I.
Apply chemical stripper. Use small 1/4" detail
brush dipped in stripper to apply material around
perimeter and spoke-like areas.
2. Remove stripper following manufacturers
recommendations.
3. Sand wheel with 240 grit while rotating wheel on
a slow spinning brake lathe or by mounting on car
and spinning by hand. This will restore the
machined appearance and promote adhesion.
CAUTION: Do not use engine power to
rotate wheel while sanding to avoid
serious personal injury.
4. Continue with "Recoating Procedure."
Recoating Procedure
1. Clean surface of contaminants.
2. Soak wheel with Amchem #33 or equivalent
from
1 to 3 minutes, then rinse with water and
blow dry.
3. Soak wheel with Amchem
#I001 or equivalent
for
1 to 3 minutes, then rinse with water and blow
dry. 4.
Finish with Ditzler Delclear Acrylic Urethane
and Ditzler Ultra-Urethane Additive or
equivalent using three coats.
1st Coat
- Light mist coat, let flash
2nd Coat
- Light, let flash
3rd Coat
- Heavy double wet coat
CAUTION: To avoid serious personal
injury when applying any two part
component paint system, follow the
specific precautions provided by the
paint manufacturer. Failure to follow
these precautions may cause lung
irritation and allergic respiratory
reaction.
5. Let dry for 24 hours - (or flash for 30 minutes,
force dry at
140" for 30 minutes, and allow to cool
for 30 minutes before mounting.
WHEEL NUT TORQUE
F Carline - M 12X 1.5 .............. 1 10 N . m (80 Ibs. ft.)

PROPELLER SHAFT $A-3
B. If companion flange run-out is over 0.15mm (.006
in.) but less than 0.28mm (.011 in.) and balance
weight is at or near low point of companion flange
run-out, no further action is required.
If balance weight is not at or near low point of
companion flange run-out, remove weight.
6. If companion flange run-out is over 0.28mm (.011
in.), but no greater than 0.38mm (.015 in.) and
balance weight is at or near low point of
companion flange run-out, no further action is
required.
If balance weight is not at or near low point of
companion flange
runout, remove weight and
reindex companion flange until run-out is 0.25
mm
(.010 in.) or less.
If impossible to achieve
0.25mm (.010 in.) or less
run-out, install a new companion flange and
recheck for
0.25mm (.010 in.) or less run-out.
Service replacement companion flanges are not
equipped with balance weights and no weights
should be added.
UNIVERSAL JOINT ANGLE MEASUREMENT
When torque is transmitted through any ordinary
universal joint, the driven yoke fluctuates slightly in
speed. In other words, although the driving yoke
rotates at a constant speed, the driven yoke speeds up
and slows down twice per revolution. This flucutation
of the driven yoke is in direct proportion to the angle
through which the universal joint is operating; the
greater the angle, the greater the fluctuation.
Whenever two universal joints are used, this
fluctuation effect can be eliminated by staggering the
joints so that the two driving yokes are 90 degrees apart
provided the two joints are transmitting torque
through the same angle.
Therefore, when two universal joints are used, the
angles through which they operate must be very nearly the
same. This allows the alternate acceleration and decelera-
tion of one joint to be offset by the alternate acceleration
and deceleration of the second joint. When the two joints
do not run at approximately the same angle, operation is
rough and an objectionable vibration is produced.
The actual optimum angles desired must take into
consideration the effects of various passenger loadings
and rear axle windup during acceleration; therefore, it
is unlikely that the front and rear universal joint angles
will be found to be the same in actual practice.
In addition, universal joints are designed to
operate safely and efficiently within certain angles. If
the designed angle is exceeded, the joint may be broken
or otherwise damaged.
The front universal joint angle is actually the
angle between the engine-transmission centerline and
the propeller shaft centerline. This angle is determined
by the design of the frame assembly and may be altered
by adding or removing shims between the transmission
and the transmission mount.
Adding one shim at the transmission mount will
decrease the transmission universal joint angle by
1/2"
and increase differential universal joint angle by 1/4".
If one shim is removed the tranmission angle will
increase
1/2" and decrease differential angle I/@. The
production transmission mount bolt is an
M10-1.5 x 35
mm. When installing two or more shims, an
M10-1.5
x 50 mm bolt must be used.
All complaints of propeller shaft vibrations
should be accompanied by rear trim height
measurements at curb weight. An incorrect trim height
may cause some vibration. If vibration is severe
enough, removal or installation of spring shims may be
required. If any irregular roughness or vibration is
detectable in the drive line, the front and rear universal
joint angles should be checked. Should the vehicle
become involved in a severe rear end collision, or
should the rear axle carrier be replaced, the rear
universal joint angle should be checked and control
arms should be replaced if necessary.
Figure 4A-6
This method can be used with the vehicle over a
pit or on a drive-on platform hoist, as long as the
vehicle is at curb weight with a full tank of gasoline.
Bounce vehicle up and down to assure curb height.
Before universal joint angles can be checked, the
measurements specified (the distance between the top
of the axle tube and the bottom of the frame) must be
met. To insure an accurate measurement, weight may
have to be added to the vehicle to reach these
specifications.
Readings should be taken at the following
locations in the following manner.
Angle Measurement at Rear Universal Joint
Figures 4A-7 and 4A-8
1. Place inclinometer J 23498-A on rear propeller
shaft bearing cap. Center bubble in sight glass and
record measurement. Bearing cap must be straight
up and down and free of dirt or other foreign mate-
rial to obtain an accurate measurement.
2. Rotate propeller shaft 90 degrees and place
inclinometer on the companion flange bearing
cap. Center bubble in sight glass and record
measurement.
3. Subtract smaller figure from larger figure to
obtain existing rear universal joint angle.
Angle Measurement at Front Universal Joint
Figures 4A.9 and 4A- 10
1. Place inclinometer on front propeller shaft
bearing cap. Center bubble in sight and record
measurement.
2. Rotate propeller shaft 90 degrees and place
inclinometer on the slip yoke bearing cap. Center
bubble on sight glass and record measurement.
3. Substract smaller figure from larger figure
lo
obtain existing front universal joint angle.

4A-4 PROPELLER SHAFT
PROPELLER SHAFT BALANCING
Hose Clamp Method
Figures 4A- 1 1 thru 4A-13
1. Place the vehicle on a twin post hoist so that the
rear of the vehicle is supported on the rear axle
housing and the rear wheels are free to rotate.
Remove both rear wheel assemblies and reinstall
wheel lug nuts with flat sides next to
drums/discs.
2. Mark and number propeller shaft at four (4)
points 90 degrees apart at rear of shaft just
forward of balance weight, as shown.
3. Install two (2) hose clamps on the rear of the
propeller shaft and slide them rearward until the
clamps stop at the nearest balance weight welded
to the tube. Align both clamps at any one of the
four marks made on shaft in Step 2 and tighten.
Be sure sufficient clearance is maintained so that
clamp heads do not contact floor pan of vehicle
when axle is in contact with rebound bumper in
frame. In order to gain sufficient clearance, it
may be necessary to position the clamps over the
balance weights.
4. Run the vehicle through the speed range to 80-90
MPH (130-145
Km/h) and note amount of
imbalance.
CAUTION: All persons should stay
clear of universal joint and balance
weight areas to avoid possible injury.
Do not run on hoist for extended
periods due to the danger of
overheating the transmission or
engine.
5. Loosen clamps and rotate clamp heads 90 degrees
to the next mark on a propeller shaft. Tighten
clamps and repeat Step 4.
6. Repeat Step 5 until car has been run with clamp
heads located at all four marks on shaft.
7. Position clamps at point of least imbalance.
Rotate the clamp heads away from each other 45
degrees (one on each side of the position), as
shown. Run the vehicle and note if imbalance has
improved.
In some cases it may be necessary to use one
clamp or possibly three clamps in order to obtain
a good balance. Replace shaft if three hose clamps
do not improve the imbalance.
8. Continue to rotate the clamps apart in smaller
angular increments until the imbalance is at its
minimum.
9. Reinstall wheel assemblies and road test the
vehicle for final check of balance. A minimal
vibration felt in the vehicle on the hoist may not
show up during a road test.
Strobe Light Method
Figures 461- 1 1, $A- 14, and 4A- 15
If a wheel balancer of the strobe light type is
available, the use of such a unit will facilitate the
balancing of the propeller shaft. The balance pick-up
unit should be placed directly under the nose of the
rear axle carrier and as far forward as possible. 1.
Place
the vehicle on a twin post hoist so the rear of
the vehicle is supported on the rear axle housing and
the rear wheels are free to rotate. Lower rear hoist
and allow axle to rest on jackstands. The groove in
the rear hoist fixture could clamp the axle and de-
stroy the sensitivity of the operation. Remove both
rear wheel assemblies and reinstall wheel lug nuts
with flat sides next to the
drums/rotors.
2.
Mark and number drive shaft at 4 points 90
degrees apart at rear of shaft just forward of
balance weights, as shown.
3. Place the strobe light wheel balancer pick-up
under the nose of the carrier.
4. Run vehicle in gear at the speed where the
distrubance is at its peak, allow the driveline to
stabilize by holding at a constant speed. Point
strobe light up at the spinning propeller shaft and
note position of one of the reference numbers.
Shut off engine and position the propeller shaft so
the reference numbers will be in the same position
as was noted while the shaft was rotating.
When strobe light flashed, the heaviest point of
the shaft was at the bottom (6 o'clock). To
balance the propeller shaft, it would be necessary
to apply the balancing weights (hose clamps) 180
degrees away from the heaviest point or at the top
of the propeller shaft (12 o'clock).
5. Install two screw-type hose clamps on the
propeller shaft as close to the rear as possible.
Position both clamp heads 180 degrees from the
heaviest point of drive shaft as indicated by strobe
light. Tighten clamps.
NOTICE: Be sure sufficient clearance is
maintained so clamp heads do not contact floor
pan of vehicle when axle is in contact with rebound
bumper on frame. In order to gain. sufficient
clearance, it may be necessary to position the
clamps over the balance weights.
6. Run vehicle through the speed range 80-90
M.P.
H. (130-145 Km/h). If disturbance is gone,
nothing further need be done on the hoist. If the
disturbance is not gone and the strobe light shows
the clamp heads at the bottom (6 o'clock) of the
shaft, go to Step
7. If the strobe light shows the
two clamp heads at the top of the shaft, add one
more hose clamp and recheck. If the strobe light
shows the three clamp heads at the top of the
shaft, remove the propeller shaft and
reindex it
180 degrees on the rear axle pinion companion
flange. Recheck with no clamps. Repeat balance
starting with Step 5. If the shaft still needs more
than three hose clamps at the same clock position,
replace it. If the clamps are also 180 degrees from
their original position after the propeller shaft
was reindexed 180 degrees, the rear axle pinion
companion flange is out of balance and must be
replaced. DO NOT use more than three hose
clamps to balance the shaft. If the strobe light
shows the hose clamps at the bottom of the shaft,
but the disturbance still exists, go to Step
7.

4819 REAR AXLE
bears against the inner race of the front bearing and a
shoulder on the pinion stem. This spacer is used to
enable accurate bearing pre-load adjustment and
maintain a pre-load on both front and rear pinion
bearings, Adjustment of the fore and aft position of the
pinion is obtained by placing a shim between the rear
pinion bearing cup and axle housing. The differential
case is of two-piece construction and is supported in
the carrier by two tapered roller side bearings. Pre-load
rear axle case by inserting shims between the bearings
and the carrier. The rear axle case assembly is
positioned for proper ring gear to pinion backlash by
varying the shim thickness from side to side. The ring
gear is bolted to the case. Two side gears have splined
bores for driving the axle shafts. They are positioned
to turn in counterbored cavities in the case. The four
rear axle pinions have smooth bores and are held in
position by a pinion cross shaft, mounted and locked
in the rear axle case. All six gears are in mesh with each
other and because the pinion gears turn freely on their
shaft, they act as idler gears when the rear wheels are
turning at different speeds. The pinions and side gears
are backed by steel thrust washers.
LIMITED-SLIP REAR AXLE
The operation of the Limited-Slip differential is
the same as the standard differential, except that there
is additional friction provided by the conical clutches.
Under ordinary driving and cornering conditions, the
cones slip, allowing the outside wheel to turn faster
than the inner. Under poor traction conditions, such as
ice, snow, or loose gravel under one driving wheel, the
increased friction provided by the cones increases the
driving torque available to the wheel with the better
traction. The cones are spring loaded to provide the
increased driving torque under extremely low traction
conditions.
Operation
When the vehicle turns a corner, the outer rear
wheel must turn faster than the inner wheel. The inner
wheel, turning slower than the outer wheel, slows its
differential side gear (as the axle shaft is splined to the
side gear) and the differential pinion gears will roll
around the slowed differential side gear, driving the
other differential side gear and wheel faster.
DIAGNOSIS AND TESTING
Many noises reported as coming from the rear
axle assembly actually originate from other sources
such as tires, road surfaces, front wheel bearings, axle
bearing, engine, transmission, muffler or body
drumming. A thorough and careful check should be
made to determine the source of the noise before
disassembling the rear axle. Noise which originates in
other places cannot be corrected by adjustment or
replacement of parts in the differential. It should also
be remembered that rear axle gears, like any other
mechanical device, are not absolutely quiet and should
be accepted as being commercially quiet unless some
abnormal noise is present.
To make a systematic check for axle noise under
standard conditions, observe the following:
1. Select a level smooth asphalt road to reduce tire
noise and body drumming.
2. Check rear axle lubricant to assure correct level,
then drive car far enough to thoroughly warm up
rear axle lubricant, approximately 10 miles.
3. Note speed and RPM at which noise occurs. Stop
car and put transmission in neutral. Run engine
slowly up and down through engine speeds,
corresponding to car speed at which noise was
most pronounced, to determine if it is caused by
exhaust, muffler roar or other engine conditions.
4. Tire noise changes with different road surfaces,
but rear axle noise does not. Temporarily
inflating all tires to approximately 50 pounds
pressure
for test purposes only will materially
alter noise caused by tires, but will not affect noise
caused by rear axle. Rear axle noise usually stops
when coasting at speeds under 30 miles per hour;
however, tire noise continues, but with lower
tone, as car speed is reduced. Rear axle noise
usually changes when comparing acceleration
and coast, but tire noise remains about the same.
Distinguish between tire noise and rear axle noise
by noting if noise varies with various speeds or
sudden acceleration and deceleration; exhaust
and axle noise show variations under these
conditions while tire noise remains constant and
is more pronounced at speeds of 20 to 30 miles
per hour. Further check for tire noise by driving
car over smooth pavements or dirt roads (not
gravel) with tires at normal pressure. If noise is
caused by tires, it will noticeably change or
disappear and reappear with changes in road
surface.
5. Loose or rough front wheel bearings will cause
noise which may be confused with rear axle
noises; however, front wheel bearing noise does
not change when comparing drive and coast.
Light application of brakes while holding car
speed steady will often cause wheel bearing noise
to diminish, as this takes some weight off the
bearing. Front wheel bearings may be easily
checked for noise by jacking up the wheels and
spinning them, also by shaking wheels to
determine if bearings are loose.
6. Rear suspension rubber bushings and spring
insulators dampen out rear axle noise when
correctly installed. Check to see that no metallic
contact exists between the spring and spring seat
opening in frame or between upper and lower
control arm bushings and frame or axle housing
brackets. The track bar and torque arm must be
bolted securely. Metal-to-metal contact at those
points may result in telegraphing road noise and
normal axle noise which would not be
objectionable if dampened by bushings.
AXLE NOISES
After the noise has been determined as being in
the axle by following the above appraisal procedure,
the type of axle noise should be determined to aid in
making repairs if necessary.

481-4 REAR AXLE
Gear Noise
Gear noise (whine) is audible from 20 to 55 mph
under four driving conditions:
1. Light Acceleration - Accelerate slowly.
2. Road Load
- Car
driving load or constant speed.
3. Float - Using enough throttle to keep the car from
driving the engine
- car slows down gradually but
engine still pulls slightly.
4. Coast - Throttle closed and car in gear.
Bearing Noise
Bad bearings generally produce more of a rough
growl or grating sound, rather than the whine typical
of gear noise. Bearing noise frequently "wow-wows" at
bearing rpm, indicating a defective pinion or rear axle
case side bearing. This noise could easily be confused
with rear wheel bearing noise. Inspect and replace as
required.
Rear Wheel Bearing Noise
A rough rear wheel bearing produces a noise
which continues with car coasting at low speed and
transmission in neutral. Noise may diminish some by
gentle braking. With rear wheels jacked up, spin rear
wheels by hand while listening at hubs for evidence of
rough (noisy) wheel bearing.
Knock At Low Speeds
Low speed knock can be caused by worn
universal joints or a side gear hub counterbore in a case
that has worn oversize. Inspect and replace universal
joint or case and side gear as required.
Backlash Clunk
Excessive clunk with acceleration and deceleration
is caused by worn differential pinion gear shaft, excessive
clearance between axle shaft and side gear splines, exces-
sive clearance between side gear hub and counterbore in
case, worn pinion and side gear teeth, worn thrust washers
and excessive drive pinion and ring gear backlash. Re-
move worn parts and replace as required, selecting close
fitting parts when possible. Adjust pinion and ring gear
backlash.
DIAGNOSIS
1. Noise
is the same in "Light Acceleration" or
"Coast".
a. Road noise.
b. Tire noise.
c. Front wheel bearing noise.
d. Rear axle bearing noise.
2. Noise changes on a different type of road.
a. Road noise.
b. Tire noise.
3. Noise tone lowers as car speed is lowered.
a. Tire noise.
b. Front
wheel bearings and rear axle bearings.
c. Gear noise.
4. Similar noise is produced with car standing and
driving. a.
Engine noise.
b. Transmission noise.
c. Exhaust noise.
5. Vibration.
a. Rough rear axle bearing.
b. Unbalanced or damaged propeller shaft.
c. Tire unbalance.
d. Worn universal joint in propeller shaft.
e. Mis-indexed propeller shaft at pinion
flange.
f. Pinion flange runout too great.
6. A knock or click approximately every two
revolutions of the rear wheel.
a. A rear axle bearing.
b. Worn case.
7. Noise most pronounced on turns.
a. Rear axle side gear and pinion noise,
differential gear noise.
b. Axle bearings.
8. A continuous low pitch whirring or scraping
noise starting at relatively low speed.
a. All bearing noise.
9. Drive noise, coast noise or float noise.
a. Ring
and pinion gear noise.
b. Front
pinion bearing noise, coast or drive.
c. Axle bearing noise.
10. Clunk
on
acceleration or deceleration.
a. Worn
rear axle pinion shaft splines.
b. Side
gear hub counterbore in case worn
oversize.
c. Worn U-joints.
d. Excessive transmission backlash.
e. Worn axle shaft splines.
11. Chatter on turns.
a. Wrong
lube in rear axle.
b. Clutch
cone worn or spalled.
12. Clunk
or knock on rough road operation.
a. Worn suspension bushings.
PRE-REPAIR INVESTIGATION AND TROUBLE
DIAGNOSIS
A carefull diagnosis of the rear axle prior to
disassembly will often reveal valuable information as to
the extent and type of repairs or adjustments necessary.
Since frequent causes of axle noises are improper
backlash, pinion bearing pre-load, or side bearing
pre-load, or a combination, a few simple adjustments
may be all that are necessary to correct a problem.
Before disassembling the rear axle, the following
checks should be made with the results recorded and
analyzed: 1) Backlash;
2) Total Assembly Preload; 3)
Tooth Contact Pattern Test; 4) Fluid Level; and 5)
Fluid Contamination.
If axle shaft end play is excessive then check
bearings, retainer, and bolts securing backing plate.
The axle bearings could be worn and need replacement.
The four bolts or nuts securing the brake backing plate
may be loose, stripped, or missing. If the inner bearing
retainer worked loose it must be replaced.
Use care at all times to keep dirt and other foreign
matter, such as grinder dust, soot or sand, away from
differential to prevent possibility of subsequent failure.

4B1-12 REAR AXLE
NOTICE: Mark differential case halves with
alignment mark before disassembly because they
could be assembled
180" off from original position.
Fig. 12 Differential Assembly Removal
3. Pry front seal out of carrier and remove bearing
cone. Discard seal.
4. Rear pinion bearing with tool J 21493-B and
press. Clamp tool around pinion shaft holding
bearing and press pinion shaft off rear pinion
bearing. (Fig. 13).
I
5. Drive rear bearing cone out of carrier with soft
brass drift, and remove selective spacer washer.
Remove or Disconnect
Four Pinion Standard Differential Assembly
(Figure
14)
1. Ring gear bolts.
1 Important
MCTICE: Left hand thread ring gear bolts.
2. Ring gear from differential housing, with soft face
hammer.
3. Drive out three differential pinion cross shaft
retaining pins.
4. Drive three differential pinion shafts from
housing, long shaft first.
5. Split differential case by holding one side and
tapping against other side with long soft drift.
6. Four differential pinions, side gears and thrust
washers from housing.
7. Differential case bearings with tool 5-22888-D
(Fig. 15).
Inspection
All components should be cleaned and inspected
for excessive wear.
Cleaning of bearings should be performed with
new solvent and should be followed up by coating
the bearing with light engine oil
to prevent
rusting.
1. I-Iypoid gear set
Important
a.
Examine for scuffed or chipped teeth. A
gear set cannot be made to run quiet if teeth
are scuffed.
b. Ring gear bore and back face should be
clean and free from burrs. The rear bearing
preload abutment faces on the
hypoid
pinion should be clean and free from burrs.
c. Examine the thread and bearing journal of
the
hypoid pinion.
2. Bearings
Important
a. Cups should have an even wear pattern and
be free from flaking or pitting. Ensure that
the abutment faces are clean and free from
burrs or raised metal.
b. The cone assemblies should feel smooth
when turned in the cups.
c. The assembly should be free from loose
particles. No cracks should be present in the
roller cages and the bores should contain no
tears.
3. Differential pinions and side gears.
Important
a. Examine the teeth for cracks and hard
contact marks. It is advisable to check the
teeth for cracks and excessive wear. The
side gear splines should be checked for
excessive wear.
b. Check the side gear journals and back thrust
for scoring.
c. The
differential pinion bores and spherical
thrust surfaces should be smooth and free
from scores.
4. Thrust washers should be free from cracks, nicks
or burrs.
5. Differential pinion cross shafts cannot be bent
and the pinion gear mating surfaces must not be
scored.

REAR AXLE 481-19
15. Press differential bearings on with tool J-21784 gear
and cone splines will occur, preventing
(Fig. 16). assembly
of remaining axle shaft. If this occurred,
16. Install assembled case into carrier following the repeat
assembly steps
11 and 12.
same procedures as developed for standard
differential.
Important
17. Installation of axle bearings and axles is the same
as standard axles. CAUTION: Do not run engine with
transmission engaged and only one
rn Important rear
wheel of vehicle elevated if rear
axle is equipped with limited slip
NOTICE:
After installing the limited slip differential. The other rear wheel will
differential in the carrier housing, be sure that both drive if in contact with the ground.
axle shafts are assembled before rotating either This action can result in damage to
axle shafts. If rotation of either axle shaft occurs the equipment or injury to the
before other is in position, misalignment of the side operator.
SPECIFICATIONS
Bolt Torque
Ring Gear Bolts
................................................................................... 13 7 N-m (101 lb. ft.)
......................................................................................... Bearing Cap Bolts 52 N-m (40
lb. ft.)
Rear Cover Bolts
........................ .. ............................................................. 26 N-m (20 lb. ft.)
........................................................................................................ Breather 14 N-m (10 Ib. ft.)
Brake Backing Plate Bolts
........................................................................... 48 N-m (36 lb. ft.)
Mounting Screws
...................... .. ............................................................... 40 N-m (30 lb. ft.)
............................................................. . Screw, Brake Line Bracket to Frame 1 1 N m (8 lb. ft.)
.......................................................... ....................... Case Half Bolt Torque 38 N.m (29 lb.
ft.)
.......................... Axle Shaft Retainer Nuts .................................... .... 46 N . m Disc (35 lb. ft.)
Bearing
Loads
Side Bearings .............................................................................. 1-3 N em (New) (10-25 lbs. in.) ' 0.5-1 N-m (Used) (6-12 lbs. in.)
............................................................. Differential Bearings 1.1-2.8 N. m (~ew) (10-25 lb.
in.)
0.5-1.4
N.m (Used) (5-12 lb. in.)
............................................................................. Hypoid Pinion 1-3 N.m (New)
(12-25 lb. in.)
0.5-1
N.m (Used) (6-12 lb. in.)
End Play
....................................... Axle Shaft (New Bearing) 0.04.mm - 0.048mm (0.001 6 - 0.0019 in.)
........................................................................ (Used Bearing) 0.076mm (0.003 in.)
Run-Out Specifications
.......................................... Differential Case/Ring Gear Mating Surface 0.05
mm (0.002") max. ................................................... ........................... Ring Gear Runout ............. 0 1 (0.005 ")
Ring Gear Backlash .......................................................... O.10mm-O.19mm (0.004 to 0.007")
Lubricant
....................... ................................................... GM Part 1050010 .. 1.7 Liters (1.8 Quarts)

REAR AXLE 4B-1
SECTION 4B
REAR AXLE
NOTICE: All rear axle attaching fasteners are an necessary.
Do not use a replacement part of lesser
important part in that they could affect the quality
or substitute design. Torque values must
performance of vital parts and systems, and/or be
used as specified during reassembly to assure
could result in major repair expense. They must proper retention
of all parts. (There is to be no
be replaced with one of the same part number or welding
as it may result in extensive damage and
with an equivalent part if replacement becomes weakening
of the metal.)
CONTENTS
General Description .................................. 4B-1
Standard Rear Axle ................... .. ............ 4B- 1
Diagnosis and Testing ............................... 4B-1
Axle Noises ......................... .. ................ 4B-3
Gear Noise ...................... .. .................. 4B-3
Bearing Noise ........................................ 4B-3
Rear Wheel Bearing Noise ....................... 4B-3
Knock at Low Speeds ............................. 4B-3
Backlash Clunk ...................................... 4B-3
Rear Axle Standard and Limited Slip .......... 4B-3
Pre-Repair Investigation and Trouble
Diagnosis
................................................. 4B-4
Gear Tooth Nomenclature ....................... 4B-4
Tooth Contact Pattern Test ..................... 4B-4
Effects of Increasing Load on
Teeth Contact Pattern
.......................... 4B-4
Adjustments Affecting Tooth
Contact
.................................................. 4B-6
Effects of Pinion Position on Tooth
Pattern
................... ... .................... 4B-6
General information ....................... .. ..... 4B-8
Limited-Slip Rear Axle ............................... 4B-8
On-Vehicle Service ............................. .. ....... 4B-8
Carrier Cover and Gasket .......................... 4B-8
............................................. Axle Shaft 4B-8
Oil Seal and/or Bearing (With
Axle Shaft Removed)
............................. 4B-9
........................................ Pinion Oil Seal 4B-9
........................................... Pinion Flange 4B- 10
..................................... Rear Wheel Bolt 4B- 1 1
.................................................... Unit Repair 4B-1 1
..................................... Rear Axle Assembly 4B- 1 1
Disassembly of Rear Axle
............................................... Assembly 4B- 1 1
.. ..................................... Case Assembly ... 4B- 12
Drive Pinion, Bearing and Races ............. 4B- 12
............................... Bearing Replacement 4B- 12
...................... Setting Drive Pinion Depth 4B- 13
........................................ Rear Axle Case 4B- 14
Side Bearing Preload Adjustment ............ 4B- 15
.................................................. Drive Pinion 4B- 16
Rear Axle Backlash Adjustment .............. 4B- 17
........... Limited Slip Rear Axle (Cone Type) 4B-17
...................................... Auburn Cone Type 4B- 18
.............................................. Specifications 4B- 19
.............................................. Special Tools 4B-20
GENERAL DESCRIPTION
STANDARD REAR AXLE Operation
The rear axle assembly is of the semi-floating type
in which the car weight is carried on the axle housing.
The rear axle assembly is designed for use with an open
drive line and coil springs. The rear axle has a
hypoid
type ring gear and pinion with the centerline of the
pinion gear below the centerline of the ring gear.
All parts necessary to transmit power from the
propeller shaft to the rear wheels are enclosed in a When
the vehicle turns a corner, the outer rear
wheel must turn faster than the inner wheel. The inner
wheel, turning slower than the outer wheel, slows its
differential side gear (as the axle shaft is splined to the
side gear) and the differential pinion gears will roll
around the slowed differential side gear, driving the
other differential side gear and wheel faster.
DIAGNOSIS AND "TESTING
salisbury type axle housing (a carrier casting with tubes Many
noises reported as coming from the rear
pressed and welded into the carrier to form a complete axle assembly actually
originate from other sources
carrier and tube assembly). A removable steel cover such as
tires, road surfaces, wheel bearings, engine,
bolted to the rear of the carrier permits service of the transmission,
muffler or body drumming. A thorough
rear axle without removing the entire assembly from and
careful check should be made to determine the
the car. source
of the noise before disassembling the rear axle.

REAR AXLE 4B-3
Noise which originates in other places cannot be
corrected by adjustment or replacement of parts in the
differential. It should also be remembered that rear
axle gears, like any other mechanical device, are not
absolutely quiet and should be accepted as being
commercially quiet unless some abnormal noise is
present.
To make a systematic check for axle noise under
standard conditions, observe the following:
1. Select a level smooth asphalt road to reduce tire
noise and body drumming.
2. Check rear axle lubricant to assure correct level,
then drive car far enough to thoroughly warm up
rear axle lubricant.
3. Note speed and RPM at which noise occurs. Then
stop car and with automatic transmission in neutral,
run engine slowly up and down through engine speeds, corresponding to car speed at which noise
was most pronounced, to determine if it is caused by
exhaust, muffler roar or other engine conditions.
4. Tire noise changes with different road surfaces,
but rear axle noise does not. Temporarily
inflating all tires to approximately 50 pounds
pressure for
test purposes only will materially
alter noise caused by tires, but will not affect noise
caused by rear axle. Rear axle noise usually stops
when coasting at speeds under 30 miles per hour;
however, tire noise continues, but with lower
tone, as car speed is reduced. Rear axle noise
usually changes when comparing acceleration
and coast, but tire noise remains about the same.
Distinguish between tire noise and rear axle noise
by noting if noise varies with various speeds or
sudden acceleration and deceleration; exhaust
and axle noise show variations under these
conditions while tire noise remains constant and
is more pronounced at speeds of 20 to 30 miles
per hour. Further check for tire noise by driving
car over smooth pavements or dirt roads (not
gravel) with tires at normal pressure. If noise is
caused by tires, it will noticeably change or
disappear and reappear with changes in road
surface.
5. Loose or rough front wheel bearings will cause
noise which may be confused with rear axle
noises; however, front wheel bearing noise does
not change when comparing drive and coast.
Light application of brakes while holding car
speed steady will often cause wheel bearing noise
to diminish, as this takes some weight off the
bearing. Front wheel bearings may be easily
checked for noise by jacking up the wheels and
spinning them, also by shaking wheels to
determine if bearings are loose.
6. Rear suspension rubber bushings and spring
insulators dampen out rear axle noise when
correctly installed. Check to see that no metallic
contact exists between the spring and spring
opening in frame or between upper and lower
control arm bushings and frame or axle housing
brackets.
Metal-to-metal contact at those points
may result in telegraphing road noise and normal axle
noise which would not be objectionable if
dampened by bushings.
AXLE NOISES
Gear Noise
After the noise has been determined as being in
the
axle by following the above appraisal procedure,
the type of axle noise should be determined to aid in
maki~~g repairs if necessary.
Gear noise (whine) is audible from 20 to
55 mph
under four driving conditions:
1. Drive - Acceleration or heavy pull.
2. Road Load - Car driving load or constant speed.
3. Float
- Using
enough throttle to keep the car from
driving the engine
- car slows down gradually but
engine still pulls slightly.
4. Coast
- Throttle closed and car in gear. Gear
noise most frequently has periods where noise is
more prominent, usually 30 to 40 mph and 50 to
55 mph.
Bearing Noise
Bad bearings generally produce more of a rough
growl or grating sound, rather than the whine typical
of gear noise. Bearing noise frequently "wow-wows" at
bearing rpm, indicating a defective pinion or rear axle
case side bearing. This noise could easily be confused
with rear wheel bearing noise. Inspect and replace as
required.
Rear Wheel Bearing Noise
A rough rear wheel bearing produces a noise
which continues with car coasting at low speed and
transmission in neutral. Noise may diminish some by
gentle braking. With rear wheels jacked up, spin rear
wheels by hand while listening at hubs for evidence of
rough (noisy) wheel bearing.
I(noclc At Low Speeds
Low speed knock can be caused by worn
universal joints or a side gear hub counterbore in a case
that has worn oversize. Inspect and replace universal
joint or case and side gear as required.
Baclclash Clunk
Excessive clunk with acceleration and
deceleration is caused by worn differential pinion shaft,
excessive clearance between axle shaft and side gear
splines, excessive clearance between side gear hub and
counterbore in case worn pinion and side gear teeth,
worn thrust washers and excessive drive pinion and
rear gear backlash. Remove worn parts and replace as
required, selecting close fitting parts when possible.
Adjust pinion and ring gear backlash.
REAR AXLE STANDARD AND LIMITED-SLIP
1. Noise is the same in "Drive" or "Coast".
a. Road noise.
b. Tire noise.
c. Front wheel bearing noise.