1988 PONTIAC FIERO transmission

PROPELLER SHAFT DlAGNOSlS
VIBRATION, ROUGHNESS, RUMBLE AND/OR BOOM
IMPACT YOKE WITH
TRANSMISSION MOUNT

4A-8 PROPELLER SHAFT
1. REFERENCE MARKS
J10011-4A-F
Figure 4A-1 1 Reference Marks on Propeller Shaft
1 2. REAR U-JOINT
1. HOSE CLAMP HEADS 2. CRAYON MARK 180" FROM CRAYON MARK
Figure 4A-12 Balance Hose Clamps in Place
1. Raise vehicle on hoist. Mark relationship of shaft
to rear axle pinion companion flange and
disconnect the rear universal joint by removing
strap bolts. If bearing caps are loose, tape
together to prevent dropping and loss of bearing
rollers.
2. Withdraw propeller shaft slip yoke from
transmission by moving it rearward and passing
it under the axle carrier.
NOTICE: Do not allow propeller shaft to drop or
allow universal joints to bend to an extreme angle,
since this may fracture the nylon injected joint
internally. Support propeller shaft during removal.
Installation
Figure 4A-13 Rotating Balance Hose Clamps
7. Rotate two of the hose clamps equally away from
each other toward the top (one on each side of the
position) in small increments until the best
balance is achieved.
In some cases it may be necessary to use one
clamp or possibly three clamps in order to obtain
a good balance.
Replace the propeller shaft if three hose clamps
do not correct problem.
8. Install wheels and road test vehicle for final check
of balance.
Vibration felt in the vehicle on the hoist may not
show up during a road test.
PROPELLER SHAFT
Removal NOTICE:
The
propeller shaft must be supported
carefully during handling to avoid jamming or
bending any of the parts.
1. Inspect outer diameter of splined yoke to ensure
it is not burred since this may cause damage to
the transmission extension housing seal and/or
bushing. Inspect splines of slip yoke for damage
or wear.
Apply lubricant to splined propeller shaft yoke and
slide yokelpropeller shaft assembly onto transmis-
sion output shaft.
Do not drive propeller shaft
in place with hammer.
Check for burrs on
transmission output shaft spline, twisted slip yoke splines, or possibly the wrong slip
yoke. Make sure that the splines agree in
number and fit. To prevent trunnion seal
NOTICE: Do not pound on original propeller
shaft yoke ears as nylon injected joints may
fracture.

PROPELLER SHAFT 4A-9
damage, do not place any tool betvveen pro-
peller shaft yoke and the universal joint
spider.
When making the rear propeller shaft connection,
be sure to align marks made on the pinion flange and
propeller shaft prior to removal.
DROP TWIN POST HOIST JUST ENOUGH TO ALLOW
THE
"V" OF THE HOIST TO CLEAR THE AXLE
THUS PLACING THE WEIGHT OF THE VEHICLE
ON THE STANDS. THE SYSTEM
WILL THEN
BE RELEASED AND FREE TO RESPOND TO
PROPELLER.
Figure 4A-14 Pick-Up Unit at Differential Pinion Nose
3. Align rear universal joint to rear axle pinion
companion flange, making sure bearings are
properly seated.
4. Install rear universal joint straps and fasteners
and torque to specifications.
UNIT REPAIR
UNIVERSAL JOINTS
NOTICE: Mark slip joint and propeller shaft to
ensure correct reassembly.
Nylon Injected Ring Type
Disassembly
Figures 4A-16,4A-18 and 4A-19
NOTICE: Never clamp propeller shaft tubing in
a vise, as the tube may be dented. Always clamp
on one of the yokes and support the shaft
horizontally. Avoid damaging the slip yoke sealing
surface. Nicks may damage the bushing or cut the
transmission extension housing seal.
1. Support the propeller shaft in a horizontal
position on line with the base plate of a press.
Place the universal joint so that the lower ear of
the shaft yoke is supported on a
1 1/8" socket.
Place Tool
J-9522-3 on the open horizontal
bearing cap and press the lower bearing cap out
of the yoke ear. This will shear the nylon injected
retaining ring on the lower bearing cap. If the
bearing cap is not completely removed, lift Tool
5-9522-3 and insert Spacer J-9522-5 between the
seal and bearing cap being removed, as shown.
Complete the removal of the bearing cup by
pressing it out of the yoke.
2. Rotate
the propeller shaft, shear the opposite
nylon injected retaining ring and press the
bearing cap out of the yoke.
3. Disengage cross from yoke and remove.
4. If the front universal joint is being replaced,
remove the pair of bearing caps from the slip yoke
in the same manner.
Assembly
Figures 4A-20 thru 4A-22
NOTICE: Production universal joints of this type
cannot be reassembled. There are no snap ring
bearing retainer grooves in production nylon
injected ring retained bearing caps.
When reassembling a propeller shaft, always
install a complete universal joint service kit. This kit
includes one
(1) pregreased cross assembly, four (4)
service bearing cap assemblies with seals, needle
rollers, washers, grease and four
(4) snap rings. Make
sure the seals are in place on the service bearing caps
to hold the needle rollers in place during handling.
Nylon injected types are replaced by external snap ring
types, unless specified otherwise in the service parts
manual.
1. Remove all of the remains of the nylon injected
bearing cap retainers from the grooves in the
yokes. The sheared nylon may prevent the
bearing caps from being pressed into place, and
thus prevent the bearing retainers from being
properly seated.
2. Install one (1) bearing cup part way into one side
of the yoke, and turn this yoke ear to the bottom.
3. Insert cross into yoke so that the trunnion seats
freely into bearing cap.
4. Install opposite bearing cap part way. Make sure
that both trunnions are started straight and true
into both bearing caps.

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.

484-18 REAR AXLE
4. With transmission in park and both wheels and
tires clear of ground, (wheels will r~tate in opp-
osite directions), measure torque required to
rotateaxle shafts with a torque
wrenchattached
to J 2619-1. If the torque reading is less than
48 N.m (35 1b.ft.) the unit should be disassembled
and repaired as required.
5. Reinstall wheel and tire assembly.
Disassemble
Limited Slip Differential.
1. Remove ring gear bolts.
NOTICE: Left hand threaded ring gear bolts.
2. Tap
ring gear off differential housing with soft
face hammer.
NOTICE: Mark differential case halves with
alignment mark before disassembly because they
could be assembled
180" off from original position.
3. Remove 8 screws holding differential housing
halves together and separate halves. 4.
Remove pinion shaft, 4 differential pinions,
thrust washers side gears, side gear shims
(if
required), spring plates, and compression springs
from housing. Discard compression springs. New
springs are required for assembly.
5. Mark each cone during disassembly to ensure
that the same brake cone will be assembled with
the same case as originally assembled. If shims
are used they must be marked so that they will be
assembled in original case half.
6. If differential bearings are damaged remove with
tool J-22888-D. (Fig. 15).
Inspect
Disassemble
The inspection procedures for the positraction
differential are the same as those for the standard
rear axle except for the side gear positioning
shims. The side gear positioning shims are used
to control case size.
1. The shims should be free of cracks, nicks, or
burrs.
2. Assemble brake cones in case and measure to
determine correct shim size. Measure the
distance from case mating surface to flat surface
on brake cone when fully seated. Select shim size
from chart below.
DISASSEMBLY INSPECTION CHART
Distance Measured mm (ins) Size
Shim Required
29.51/29.34 (1.162/1/155) no shim required.
29.64/29.54 (1.167/1.163) 0.13 (.005) shim required.
29.77D9.67 (1.172/1.168) 0.25 (.010) shim required.
Assemble
Limited Slip Differential
1.
Lubricate both sides of pinion thrust washers,
pinion bores and differential pinion shafts with
specified rear axle lube before assembling.
2. Install the 4 pinions and spherical thrust washers.
3. Replace original brake cone, shim if required, and
side gear in cap half of differential case. For shim
selection, if needed, refer to Disassembly
Inspection Chart. Apply mixture of molybdenum
disulphide and specified axle oil to face of side
gear.
NOTICE: Do not 1.eplace cone or case
independently. They must be replaced as a unit
together.
4. Install spring
plate on side gear with convex side
towards flange half.
5. Assemble differential pinion shaft, pinions, and
spherical thrust washers into cap half of
differential case with pinions meshing with side
gear. 6.
Install three new concentric thrust springs
through the center of the pinion shaft spider.
7. Assemble second spring plate and springs with
cgnvex side towards springs.
8. Coat other side gear face with molybdenum
disulphide and axle lubricant and install side gear
shim if required. Install brake cone on spring
plate.
9. Install
flange half of case on top of assembly with
oil channels aligned.
10. Install
two bolts through cases
180" apart and
tighten finger tight.
11. Axle shafts are used to align the side gear and
brake cone splines. Put a clamp on one axle shaft
so 75 mm (3 inches) extends beyond clamp.
Install differential housing onto axle shaft splines,
flanged half first.
12. Install other axle shaft through cap side of
differential case and align side gear and cone
splines.
13. Install remaining
bolts and tighten to specified
torque.
14. Install
ring gear and tighten bolts to specified
torque.

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.