wheel OPEL GT-R 1973 Repair Manual

WHEELS AND TIRES36-63would require inflation pressures above the maximum allowable, speed must be
limited to 75 miles per hour.
3.Cool tire inflation pressure: After vehicle has been inoperative for 3 hours
or more, or driven less than one mile. Hot tire inflation pressure: After vehicle
has been driven
10 miles or more at 60-70 MPH.
4.Vehicles with luggage racks do not have a vehicle load limit greater than
specified.
5. When towing trailers, the allowable passenger and cargo load must be
reduced by an amount equal to the trailer tongue load on the trailer hitch.
Torque SpecificationWheelNuts
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65lb.ft.
IFigure 3G-8 Wheel and Tire - Exploded View

4S- 91973 OPEL SERVICE MANUAL
DIAGNOSIS
DIFFERENTIAL TROUBLE DIAGNOSISConditionPossible Cause
1. Noise is the same in1. a) Road noise.
“Drive” or “Coast”.b) Tire noise.
c) Front wheel bearing noise.
d) Front or rear U-joint angle
too great.
2. Noise changes on a2. a) Road noise.
different type of road.b) Tire noise.
3. Noise lowers tone as3. Tire noise.
car speed is lowered.
4. Similar noise is pro-4. a) Engine noise.duced with car standingb) Transmission noise.
and driving.c) Driveline angle.
5. Vibration5. a) Rough rear wheel bearing.
b) Tire unbalance.
c) Worn universal joint in
propeller shaft.
d) Front or rear U-joint angle
too great.
e) Mis-indexed, propeller shaft
at companion flange.
tJ Companion flange runout too
6. A knock or click6. A brinelled rear wheel bearing
approximately every two (2)
revolutions of rear wheel.
7. Noise most pronounced on7. Differential side gear and pin
turns.
8. A continuous low pitch8. Pinion bearing.
whirring or scraping noise
starting at relatively low
speed.9. Drive noise, coast9. Ring and pinion gear.
noise or float noise.
10. Clunk on accelera-
10. a) Worn differential cross sha
tion or deceleration.in case.
11. Groan in “Forward” or11. Wrong lube in differential.
“Reverse”.
12. Clunk or knock on12. a) Excessive end play of axle
rough road operation.to differential cross shaft
b) Excessive differential gear
clearance.

REAR AXLE48. 9
MAJOR REPAIRREMOVAL AND INSTALLATION OF REAR AXLE
ASSEMBLYRemoval
1. Raise rear of car with floor jack under differential
carrier and position jack stand under jack bracket on
each side of car. Remove rear wheel assemblies and
one brake drum.
2. Disconnect parking brake cable equalizer and re-
turn spring from brake rod.
3. Detach parking brake cable from actuator lever
and backing plate at wheel with brake drum
removed. Disconnect cable from lower control arm
brackets and pull loose end over exhaust system.
4. Disconnect shock absorbers at lower end.
5. Disconnect track rod at left end.
6. On cars equipped with a stabilizer rod, disconnect
the shackles at rear axle housing.7. Disconnect universal joint from pinion flange and
support or tie propeller shaft out of way after mark-
ing mating areas. If propeller shaft is removed, install
plug in rear of transmission to prevent loss of lubri-cant.8. Disconnect brake hose from brake pipe at differen-
tial and remove retaining clip.
9. Lower rear axle assembly far enough to remove
coil springs.
10. Remove central joint support bracket to under-
body retaining bolts.
11. Disconnect lower control arms at rear axle assem-
bly bracket and roll the assembly from under the car.
See Figure
4B-2.Installation
CAUTION: Fasteners in the following steps are impor-tant attaching parts in that they could affect the
performance of vital components and systems, and-
/or coo/d
resuJt in major repair expense. They must
be rep/aced with one of the same part number or withREAR SHOCK ABSORBERS
SPRING SEAT
4B-1Figure
4B-l Differential and Rear Suspension Assembly

4B- 101973 OPEL SERVICE MANUAL
Figure 48-Z Removing Rear Axle Assemblyan equiva/entpart ifreplacement becomes necessary.
Do not use a replacement
part of lesser quality or
substitute design. Torque
values must be used as
specified
during reassembly to assure proper reten-
tion of these parts.1. Roll rear axle assembly under car on floor jack and
loosely attach lower control arms to rear axle hous-
ing.
2. Attach central joint support, to underbody with
bolts only finger tight.
3. Lower rear axle assembly, install lower damper
rings in spring seats, coil springs and upper damper
rings on springs. Make certain the damper rings and
springs are properly positioned.
4. Install track rod on axle housing.
5. On Opel 1900 and Manta, place a load of approxi-
mately 350
Ibs. in luggage conipartment or on the
GT, place a load of approximately 150 lbs. on drivers
seat and raise rear axle far enough for underbody to
clear jack stands.
6. Torque central joint support t$ underbody bolts to
36 lb.ft.
7. Torque lower control arm to
Axle housing bolts to
18
Ib.ft. on the GT and 22 lb.ft. dn the Opel 1900 and
Manta.
8. Torque track rod to rear axle attaching nut to
40lb.ft. on the GT and to 76
lb.ft. on the Opel 1900 and
Manta and remove added weight.
9. Install shock abosrbers and tighten nuts to 15
Ib.ft.on the GT and to 47
Ib.ft. on the Opel 1900 and
Manta.10. If car is equipped with stabilizer rod, connect
shackles to axle housing. Tighten to 25 lb. ft.
11. Connect brake hose to brake pipe and install
retaining clip.
12. Thread parking brake cable over exhaust system
and connect to lower control arm brackets, parking
brake actuating lever and brake backing plate. Install
brake drum.
13. Align mating marks and connect propeller shaft
to pinion flange. Tighten universal joint attaching
bolts to 11
Ib.ft. Bend respective lock plate tabs to
secure nuts or bolts.
14. Connect parking brake cable equalizer and return
spring to brake rod and adjust to specifications.
15. Bleed rear brake system and fill master cylinder.
16. Install wheel assemblies and tighten lug nuts to
65
lb.ft.17. Remove jack stands and lower car to the floor.
REMOVAL AND INSTALLATION OF AXLE SHAFT
ASSEMBLY
Removal1. Raise and support rear of car at jack brackets.
2. Remove wheel and brake drum as necessary.
3. Unscrew rear axle shaft retaining plate and with
axle shaft puller J-8805 coupled with slide hammer
J- 2619 on axle shaft flange, remove axle shaft.
4. For replacement of the bearing parts, first remove
retaining ring by cutting off with a chisel. See Figure4B-3.
5. Press off bearing, using rear pinion bearing
remover J-22912.
Installation
CAUTION: Fasteners in the following steps b are im-
portant attaching parts in that they could at&t
tee
performance of vital components and systems, and-
/or could result in major
repair expense.They must
be replaced with one of the same part number or with
an equivalentpart ifreplacement becomes necessary.
Do not use a replacement part of lesser quality or
substitute design Torque values must be used as
specified
during reassembly to assure proper reten-
tion of these parts.1. Check radial runout of axle shaft at ball bearing

REAR AXLE40- 11
Figure
48-3 Removing Axle Bearing Retaining Ring
seat and lateral runout of axle shaft flange near larg
est diameter.
Permissible radial runout is .002”, and permissible
“lateral runout is
.OO4”. An axle shaft which exceeds
these tolerances, or one which has been otherwise
damaged during removal, must be replaced.
2. Using installer ring J-21721-2, press on bearing so
that oil seal groove on bearing faces shaft splines.
3. Using installer ring J-21721-2, press on retainer
ring so that shoulder faces bearing.
Figure 48.4 Measuring for Axle Shaft Bearing Depth4. Check axle shafts end play as follows:
a. Using a depth gauge, measure depth of rear axle
bearing seat in axle housing (backing plate and gas-
kets in place). See Figure
4B-4.b. Measure width of bearing outer race. The differ-
ence between the two measurements indicates the
required thickness of the shims. The maximum per-
missible end play is .002”. If necessary to reduce end
play, add
,004” shims behind bearing as necessary. A
slight crush fit (up to ,006”) is desirable.
5. Coat rear axle shaft splines with hypoid gear lubri-
cant prior to installation.
6. Insert axle shaft into housing; using a mallet, drive
axle shaft completely into housing.
7. Install lock washers and nuts. Torque to 20
Ib.ft.8. Install brake drum and wheel assembly.
9. Remove supports and lower rear of car to floor.
DISASSEMBLY AND ASSEMBLY OF THE
DIFFERENTIALRemoval and installation of parts for service de-
scribed in the following sub-paragraph can be per-
formed with the rear axle assembly in the car. The
car must be raised and adequately supported to per-
mit access to the parts to be serviced.
Removal and Disassembly of Differential Case1. With car suitably supported at rear jack bracket
on each side, remove differential cover bolts and let
lubricant drain into suitable container.
2. Disconnect left end of track rod and wire to left
shock absorber.
3. Remove both rear wheels and brake drums.
4. Working through access holes in axle shaft flange,
remove four nuts and washers that retain the axle
shaft dust shield and brake backing plate to the axle
housing.
5. Unscrew rear axle shaft retaining plate.
6. Install axle shaft puller J-8805 coupled with slide
hammer J-2619 on axle shaft flange to remove rear
axle. In removing axle shaft, care should be exercised
to avoid damage to the oil seal. See Figure
4B-5.7. Remove differential cover and discard gasket.
8. Check and record ring gear backlash.

POWER BRAKE BOOSTER AND MASTER CYLINDER5A- 5ConditionGrabby Brakes (Apparent
Off-and On Condition)
Possible Cause1. Broken or damaged
hydraulic brake lines.Correction1. Inspect and replace, as
“CXXSSary.2. Insufficient fluid in
master cylinder.
3. Defective master cylinder
seals.4. Cracked master cylinder
casting.2. Fill reservoirs with approved
brake fluid check for leaks.
3. Repair or replace, asnecessary.4. Replace
5. Leaks at front disc brake
calipers or rear wheel
cylinders
in pipes or connections.5. Inspect and repair, as
necessary.Brakes Fail to Release6. Air in hydraulic system.
1. Blocked passage in power
piston.
2. Air valve sticking shut.6. Bleed system.
1. Inspect and repair or replace,
as necessary.
2. Check for proper lubrication of
air valve “0” ring.
3. Broken piston return spring
3. Replace
master cylinder.
4. Tight pedal linkage.5. Repair or replace, as
necessary.
MAINTENANCE AND ADJUSTMENTS
CHECKING BRAKE BOOSTER OPERATIONThe operation of the brake booster can be checked by
simple means and without any special devices.
1. With engine off, first clear the booster of any
vacuum by depressing brake pedal several times.
2. Then depress brake pedal and start engine. If the
vacuum system is working correctly, the brake pedal,
kept under even foot pressure, moves farther down-
wards due to the additional pressure developed by
the booster. Should the brake pedal not move farther
downwards, the vacuum system is deficient. In this
case check the vacuum hose to booster, to vacuum
control valve and to engine intake manifold connec-
tions.3. If the vacuum system operates properly, the defect
is in the brake booster itself. A dirty filter impairs oreven prevents air from entering into the booster and
thereby the formation of a difference in pressure in
the vacuum cylinder.
Repairs cannot be carried out on the brake booster.
If no deficiency can be found in the vacuum system
or filter, the brake booster has to be replaced.
Under normal operating conditions the brake
booster requires no service. However, under adverse
conditions such as frequent driving on sandy or
dusty roads, the filter and sound deadener should be
replaced occasionally. To do so, the brake booster
must be removed but it isn’t necessary to detach the
master cylinder.
BRAKE BOOSTER FILTER SERVICEUnder normal operating conditions the filter need
not be exchanged for a new one.
Under adverse operating conditions
- frequent driv-

5B- 10 1973 OPEL SERVICE MANUAL
DISC BRAKES
CONTENTS
Subject
DESCRIPTION AND OPERATION:
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Operation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . . . . . . . . . . . . .DIAGNOSIS:
DiscBrakeTroubleDiagnosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MAINTENANCE AND ADJUSTMENTS:
Disc Brake Maintenance
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Checking Disc Brake Friction Pads for Wear
. . . . . . . . . .Replacing Friction Pads
Checking Brake Disc for Lateral
Runout. . . . . . . . . . . . . . . . . .MAJOR REPAIR:
RemovingandInstallingBrakeCaliper. . . . . . . . . . . . . . . . . . . . . .Removing and Installing Brake Disc
. . . . . . . , . . . . . . . . . . . . . . . . . .
RemovingandInstallingBrakeDiscShield. . . . . . . . . . . . . .Disassembly and Assembly of Brake Caliper
. . . . . . . . . .SPECIFICATIONS:
Disc Brake Specifications
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page No.
58-1058-l
1
58-12
58-15
SB-15
5&17
56-17
58-17
58-195519
58-21
DESCRIPTION AND OPERATION
DESCRIPTIONThe front wheel disc brake consists of two major
parts: The brake disc and the brake caliper with the
two friction pads. See Figure
5B-20.The brake disc is attached to the inside of the wheel
hub flange by four bolts and centered on a shoulder
of the hub. The brake caliper consists of two halves:
the mounting half, arranged on the inside of the
brake disc, and the rim half. The two halves are
firmly attached to each other by four bolts. Two
flanges on the mounting half serve as attachment of
the brake caliper to the steering knuckle. The brake
caliper is positioned behind the front suspension
cross member at steering knuckle spindle level. It is
attached to the steering knuckle by two bolts. Both
caliper halves act as brake cylinders and each houses
a piston and a fluid seal. The fluid seal, of square
cross section, is positioned in an annular groove of
the caliper bore, preventing fluid leakage past the
piston and entry of water and dirt. The pistons and
caliper half bores are protected against entry of waterFigure 58.20 Left Front Disc Brake Assembly
and dirt in brake disc direction by a rubber seal, held
on the caliper half collar by a clamp ring and against

DISC BRAKES5B- 11
rLF 5.2. RUBBER FLUID SEALS6.3. HOLLOW PISTONS7.
AL5
3Figure 58.21 Left Front Disc Brake
- Emloded View
the piston circumference by its inherent tension. See
Figure
5B-21. Both pistons are hollow. The open end
of each piston faces the brake disc.
A sheet metal spacer plate with two impressions for
preventing the piston from rotating is installed be-
tween each piston and friction pad and secured by
the friction pad dowel pins. The two friction pads are
positioned on the right and left of the brake disc
recesses in the caliper halves. Each friction pad con-
sists of a backing plate with friction material, which
is abrasive-coated, bonded to it. The friction pad
assemblies are held in position in the brake caliper by
two dowel pins, secured by slit dowel pin retainers,
and by a cross-shaped retaining spring which is pre-
loaded and positioned under the dowel pins, thus
pressing the friction pads and spacer plates firmly
against the pistons. The front brake line leading from
the brake master cylinder attaches to a distribution
tee from which a brake line leads to each front wheel
caliper. The caliper bores are interconnected by fluid
ducts within the caliper halves.
The front wheel disc brakes have self-adjusting pis-
tons. See Figure
5B-22.The adjustment of the pads is effected by the pistons
which push the friction pads ahead towards the
brake disc for a distance equivalent to the amount of
friction pad wear. This means that the greater the
wear the closer the pistons move towards the brake
disc. A running clearance exists between friction
pads and brake disc when the brakes are in “off”
position. This running clearance is provided by the
rubber fluid seals which are positioned in the caliper
half bores and which tightly grip and exert their
pre-load pressure on the pistons. The rubber fluid
seals also prevent the pistons from being pushed into
the caliper half bores more than the distance equiva-
lent to the running clearance. As the friction pads are
adjusted by the pistons, there must be no static pres-
sure in the front brake circuit when the brakes are in“OR position. Non-existence of a static pressure in
the front brake circuit is achieved by eliminating the
check valve in the brake master cylinder on the front
brake circuit. During brake application the pressure
from the brake master cylinder is transferred to the
pistons in the brake caliper. The pistons move ahead
and press the friction pads against both friction
SW-faces of the rotating brake disc. The force exerted on
the brake pedal determines the pressure of the fric-
tion pads against the brake disc. On releasing the
brake pedal, the brake lines of the front brake circuit,
including the caliper half bores, are relieved of
hy-OPERATION

DISC BRAKES5B- 13
Condition
Possible CauseCorrection
2. Front end out of line.2. Check and align to manufac-
turer’s specifications.
3. Unmatched tires on sameaxle.3. Tires with approximately the
same amount of tread should be used
on the same axle.
4. Restricted brake tubes
or hoses.4. Check for soft hoses and damaged
lines. Replace with new hoses and
new double-walled steel brake
tubing.
5. Malfunctioning caliper
assembly.5. Frozen caliper
- check for
stuck or sluggish pistons, proper
lubrication.
6. Defective or damaged
shoe and lining (grease or
brake fluid on lining or
bent shoe).6. Install new shoe and lining in
complete axle sets.
7. Malfunctioning rear
brakes.7. Check for brake adjustment,
defective lining (grease or brake
fluid on lining) or defective wheel
cylinders. Repair as necessary.
8. Loose suspension parts.
9. Loose calipers.8. Check all suspension mountings.
9. Check and torque bolts to
specifications.
Brake Roughness or Chatter
(Pedal Pulsates)
1. Excessive lateralrunout.1. Check per instructions and
replace or machine the rotor, if not
within specifications.
2. Parallelism not within
specifications.2. Check per instructions and replace
or machine the rotor, if not within
specifications.
3. Wheel bearings not
adjusted.3. Adjust wheel bearings to correct
specifications.
4. Rear drums out of round.4. Check runout and, if not within
specifications, turn the drums within
specifications.
5. Shoe reversed (steel
against iron).5. Replace shoe and lining and
machine rotor within specifications.
ExcesGve Pedal Effort1. Malfunctioning power
brake.1. Check power brake and repair,
if necessary.

DISC BRAKES5B- 15
ConditionPossible Cause
2. Binding brake pedal
mechanism.Correction
2. Check and lubricate, ifnecessary.3. Corroded caliper
assembly.3. Clean and lubricate.
MAINTENANCE AND ADJUSTMENTSDISC BRAKE MAINTENANCE
Checking Brake Fluid Level
The brake fluid level in the brake fluid container
must be checked during predelivery inspection, then
every 3,000 miles during inspection and preventive
maintenance servicing.
The brake fluid level must not be higher than the
inscription “MAX” and must be at least up to
“MIN”. Replenish brake fluid, if necessary.
Because of the relatively large brake caliper bore
cross section and the self-adjustment of the disc
brakes, resulting in a greater piston travel to compen-
sate for friction pad wear, the brake fluid level drops
faster than in fluid containers for drum brakes with
their smaller wheel brake cylinders. For this reason
pay special attention to the fluid level in the brake
fluid container.
Drop of brake fluid level can be due to friction pad
wear and may not be due to leakage in the braking
system.On loss of brake fluid due to leakage, the brake sys-
tem must be checked thoroughly.
Friction Pad Adjustment
Friction pad adjustment is not necessary on the front
wheel disc brakes as this is done automatically by the
pistons in the brake calipers.
Lubricating Front Wheel Bearings
When removing one or both brake discs, check lu-
brication of front wheel bearings and the cavity of
the wheel hub and replenish if necessary (see operat-
ion
“Removing and Reinstalling Brake Disc”).
When carrying out other work on disc brakes which
does not necessitate the removal and installation of
the brake disc, lubricating wheel bearings is not
necessary.Checking Disc Brake Friction Pads for Wear
Whenever a disc brake equipped car is in for periodic
service, while the car is raised, the friction pads in
both brake calipers should be checked for wear by
making a simple measurement. Worn or oily friction
pads must be replaced.
Measure friction pad wear as follows:
1. Remove friction pads.
2. Using a one-inch micrometer, measure the thick-
ness of the pad and friction plate. See Figure
5B-23.Figure 58-23 Checking Brake Friction Pad Thickness
3. If any one of the four measurements is less than
-.280, replace all four friction pads. (Partial replace-
ment of friction pads would cause unequal braking.)
Removal and Installation of Friction Pads
1. Raise car and remove front wheels.
2. Drive dowel pins out of brake calipers toward
center of car. See Figure
5B-24. Dowel pins must be
driven inward because they are secured by enlarge
fluted inner ends.
3. Remove friction pads from brake calipers. See
Figure
5B-25.