1973 OPEL GT-R brake

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.

BRAKES
GROUP 5
Section
5A
5B
5C
Title
Brake Booster and
Master Cylinder
Disc Brakes
.._.__.._____
Drum Brakes. . . . . . . . . . . . .
Page No.
5A- 2
5B-10
5C-22

CONTENTS
SubjectPage No.
DESCRIPTION AND OPERATION:
Power
BrakeBooster. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Master
Cylinder
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DIAGNOSIS:
Power
Brake
,UnitTroubleDiagnosis. . . . . . . . . . . . . . . . . . . . . . . . . .MAINTENANCE AND ADJUSTMENTS:
Checking Brake Booster Operation
. . . . . . . . . . . . . . . . . . . . . . . . . . . .Brake Booster Filter Service
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Vacuum Control Valve Service
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MAJOR REPAIR:
5A-2
5A-2SA-4SA-5
5A-65A-6
Brake Booster Removal and Installation
. . . . . . . . . . . . . . . . . .Master Cylinder Overhaul
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . . . . . .SPECIFICATIONS:
General
Specifications
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SA-6
5A-7
5A-95A. 21973 OPEL SERVICE MANUAL
POWER BRAKE BOOSTER AND MASTER CYLINDER
DESCRIPTION AND OPERATION
POWER BRAKE BOOSTERThe vacuum power cylinder contains the power pis-
ton assembly which houses the control valve and
reaction mechanism and the power piston return
spring. The control valve is composed of the air valveand the floating control valve assembly. The reaction
mechanism consists of a hydraulic piston, reaction
plate, and a series of springs. An air filter element is
assembled around the push rod and fills the cavity
inside the hub of the power piston. This keeps dirt
and dust from entering the vacuum booster. The
push rod, which operates the air valve, projects out
of the end of the power cylinder ‘housing through a
boot.MASTER CYLINDER
The master cylinder is composed pf a primary pistonand secondary piston; it is supplied with fluid from
two separate reservoirs. A check valve is mounted onthe primary circuit which supplies fluid to the rear
brakes. This keeps a slight static pressure in the rear
brake system. When the pedal is depressed, the pushrod moves the two pistons forward simultaneously
until the seals of the two pistons cover the compen-
sating ports in the cylinder. The pressure is increasedin the two chambers simultaneously, thus supplying
fluid to both front and rear brake systems.Figure
5A-1 Brake Booster Attachment (Opel 1900
and Manta)
In the GT, the brake fluid container is arranged at
right angles to the tandem brake master cylinder. SeeFigure
5A-3. It is pushed over the feed port of the
rear brake circuit onto the brake master cylinder and

POWER BRAKE BOOSTER AND MASTER CYLINDER5A- 3
Figure 5A-2 Exploded View Master Cylinder (Opel 1900 and Manta)
held in position by a retaining plate. The front brake
circuit is connected to the brake fluid container by a
hose and a connector. See Figure
5A-4.An offset brake actuating rod, consisting of pedal
rod, adjuster and connecting tube, is used between
the brake pedal, the tandem brake master cylinder
and brake booster respectively. The connecting tube
is pressed onto the pedal rod and adjuster. The speci-
fied brake pedal free travel of
l/4 inch is obtained by
adjusting the brake booster piston rod and lock nut
of the adjuster.
VACUUM CONTROL VALVEhose between the intake manifold and the brake
booster and serves to prevent air from flowing back
(vacuum release) when the engine is shut off. See
Figure 5A-5.
This valve cannot be disassembled andmust be replaced when defective. To do this, the
short hose should be used between the intake mani-
fold and the vacuum control valve and the long hose
between the vacuum control valve and the brake
booster. Arrows on the valve housing indicate its
correct position in the line. Should a vacuum control
valve be installed backward no air could be drawn
out of brake booster, thus rendering it inoperative.
Hose clamps should be installed to prevent the possi-
bility of vacuum leaks.
A vacuum control valve is installed into the vacuum

5A- 41973 OPEL SERVICE MANUAL
Figure
5A-4 Brake Pedal and Master Cylinder
Attachment
(GT)
v1I cy
1 THRUST SPRING
2 VALVE SEAT
3 HOUSING
Figure
5A-5 Vacuum Control Valve
DIAGNOSIS
POWER BRAKE UNIT TROUBLE DIAGNOSIS
ConditionPossible Cause
CorrectionHard Pedal
1. Broken or damagedhydraulic
brake lines.
1, Inspect and replace as necessary.
2. Vacuum failure.
2. Check for:a) Faulty vacuum check valve or
grommet
- replace.
b) Collapsed or damaged vacuum
hose
- replace.
c) Plugged or loose vacuum
fitting
- repair.
d) Faulty air valve seal
drsupport plate seal
- replace.
e) Damaged floating control valve.
3. Defective diaphragm.
4. Restricted air filter
element.3. Replace
4. Replace5. Defective apply piston5. Repair and replace master
seals.cylinder.
6. Cracked or broken powerpistons or retainer.6. Replace power unit.

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-