1973 OPEL GT-R lock

49- 201973 OPEL SERVICE MANUAL
IN.LB. TORQUE
Figure 48.30 Checking Side Bearing Preload
4. With the use of a feeler gauge, check clearance
between differential side gears and case. See Figure
4B-31. Clearance should be ,003” to X106”. If clear-
ance is not within these limits, remove side gears and
install shims of correct thickness to obtain desired
clearance, reassemble and install pinion shaft lock
pin.
Figure 48.31 Checking Side Gear to Case Clearance
5. Install ring gear on case, making certain their
mating surfaces are free of burrs or foreign material.
Tighten bolts to 47
lb.ft.
6. Check lateral runout of installed ring gear. Max- imum permissible

runout is X03”. If runout is
greater than specified, make certain that dirt or burrs
are not holding the ring gear in a cocked position on
the case and that the bolts are evenly torqued.
7.
Imtall side bearings using Installer J-22919 and
Drive Handle J-8092. Support opposite side of case
on Pilot J-2241-1 1 to prevent bearing damage. See
Figure
4B-32.
DRIVER
HANDLE
J-8092
4B.27
Figure 48-32 Installing Differential Side Bearings
Figure
48.33 Installing Differential Case Assembly

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

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-

5A- 61973 OPEL SERVICE MANUAL
ing on dusty and sandy roads - the filter and sound
deadener should occasionally be replaced. To do so,
brake booster has to be removed without detaching
brake master cylinder.
Proceed as follows:
1. Remove protective cap (boot).
2. On the GT only, pry retainer from housing
using a screwdriver. See Figure
SA-6.Figure 5A-6 Brake Booster Filter (GT)
3. With a pointed tool remove air silencer and filter
out of control housing bore and pull it off thrust rod.
4. Install new filter and air silencer. On the GT, the
smooth side of the filter must face towards the inside.
The radial slots in filter and deadener must be stag-
gered to each other by 180 degrees.
5. Slide retainer over control housing (GT only) and
seal it with light plastic hammer strokes. Slide pro-
tective cap over control housing and slip it onto
brake booster housing.
VACUUM CONTROL VALVE SERVICE
A vacuum control valve is installed into the vacuum
hose between intake manifold and brake booster. It
serves to prevent air from flowing back (vacuum
release), when engine is shut off.
The vacuum control valve cannot be disassembled
and has to be replaced, if defective. On replacement,
note the following:
1. The vacuum control valve should be located near
the intake manifold. Therefore, the short vacuumhose has to be installed between intake manifold and
vacuum control valve and the long hose between
vacuum control valve and brake booster.
2. The arrows on the vacuum control valve housing
must point towards the intake manifold, otherwise
no air can be drawn out of the brake booster which
renders the brake booster ineffective.
3. The connections of the vacuum hoses to the intake
manifold, vacuum control valve and brake booster
must be airtight. For this reason make sure. that the
hose clamps are properly installed.
MAJOR REPAIR
BRAKE BOOSTER REMOVALAND INSTALLATION
Removal
1. Disconnect brake pipes from master cylinder.
Place a cloth under the master cylinder and brake
pipes to absorb any brake fluid drippings.
2. Disconnect vacuum hose from brake booster.
3. Remove four nuts and washers attaching brake
booster to brake booster support.
4. On the GT only, remove master cylinder support
to fender skirt bolts.
5. On the GT, loosen thrust rod lock nut and un-
screw the piston push rod while holding the master
cylinder brake booster assembly. On the Opel
1900and Manta, remove the nut and bolt attaching clevis
on the pedal.
6. Remove assembly from car.
7. Disconnect master cylinder from brake booster.
Installation
CAUTION: Fasteners in the folkwing steps are im-
portant attaching parts in that they could affect the
performance of vital components and systems, and-
/or could result in major repair expense. They must
berep/aced, with one of the same part number or with
an equivalent part if replacement becomes necessary.
Do not
use a replacement part or lesser quality or
substitute design. Torque values must be used as
specified during reassembly to assure proper reten-
tion of these parts.1. Using a new front housing seal, assemble master

POWER BRAKE BOOSTER AND MASTER CYLINDER5A- 7cylinder to brake booster and torque nuts to 14
Ib.ft.on the GT and 12
lb.ft. on the Opel 1900 and Manta.
2. Position assembly into brake booster bracket and,
on the GT only, thread piston push rod onto the
thrust rod.
3. Install brake booster to support attaching washers
and nuts and tighten to 11
lb.ft. of torque.
4. On the GT install master cylinder support to inner
fender skirt bolts.
5. Connect vacuum hose to brake booster.
6. By turning the piston push rod on the thrust rod,
(GT only) adjust until the brake pedal free travel is
l/4 inch and tighten the lock nut.
7. Connect brake pipes to master cylinder and bleed
brakes.
MASTER CYLINDER OVERHAUL. GT
Removal of Master Cylinder1. Disconnect the two brake pipes from the master
cylinder.
2. Remove the front support to skirt attaching bolts,
the cylinder to booster retaining nuts and lift out
master cylinder.
Disassembly1. Prior to brake master cylinder disassembly, pour
brake fluid out of brake fluid reservoir, remove reser-
voir from master cylinder and take sealing plugs out
of housing.
2. Screw static pressure valve(s) out of housing.
3. To facilitate disassembly, push piston somewhat
into cylinder and insert a rounded off piece of weld-
ing rod approx.
.12 in. thick into feed port to retain
piston in this position.
4. Remove stop screw and snap ring out of housing
and take out both pistons together with springs.
5. Remove stop screw from piston for rear brake
circuit and remove all component parts. Remove
also all component parts from intermediate piston of
front brake circuit.
Cleaning and Checking1. Clean parts with genuine brake fluid, Delco Su-
preme No. 11, or equivalent. Do not use any other
cleaning solvents. Dry with compressed air. Free up
compensating and feed ports.2. Polish cylinder bore of housing with crocus cloth.
If lapping scores and rust spots are still noticeable,
replace brake master cylinder assembly.
3. Check inner components for damage and replace,
if required. The rubber seals and static pressure valve
always have to be replaced.
Assembly1. Assemble front and rear brake circuit pistons.
Prior to assembly coat rubber seals with brake fluid.
2. Coat cylinder bore, piston sliding surfaces and
seals with brake fluid.
3. Insert preassembled intermediate piston for front
brake circuit together with thrust spring and spring
seat into clyinder bore. The smaller diameter of the
tapered thrust spring must face piston.
4. With a drift, push piston (against spring pres-
sure) into housing and insert a piece of welding rod
into feed port of front brake circuit to retain piston.
5. Install stop screw with new seal ring into housing
and tighten.
6. Insert preassembled piston for rear brake circuit
into cylinder bore and install snap ring into groove
in housing.
7. Check piston fof free movement by moving it to
and fro. If required, place washers under the head of
the stop screw.
8. Lightly push piston into housing and remove
piece of welding rod out of feed port of front brake
circuit.
9. With a rounded off piece of welding rod
(.020 -
,024 in.) check whether compensating ports are free.
10. Screw in new static pressure valve(s).
11. Coat new sealing plugs with brake fluid and in-
sert them into housing. Push twin brake fluid con-
tainer into sealing plugs and install screen and cover
with seal ring.
Installation1. Install master cylinder onto brake booster with
washers and nuts. Torque to 14
lb.ft.2. Attach the front mounting bracket.
3. Install brake lines on master cylinder, and bleed
brakes.

58-181973 OPEL SERVICE MANUAL
Figure 58.28 Brake Caliper
to Steering Knuckle
Attaching Bolts
wheel. Disconnect brake caliper with friction pads
from steering knuckle and support the assembly as
shown in Figure
5B-29.Figure 58.29 Supporting Brake Caliper
2. Remove front wheel hub and disc assembly along
with wheel bearings.
3. Mount brake disc and wheel hub between soft
metal jaws in vise.
Do not hold too tightly, to avoidbending whet-1 bolts. Remove four star head bolts
with lockwashers using Star Wrench Adapter
J-
21737.
Piior to removal, markposition ofbrake disc
in relation to wheel hub. See
Figure 5B-30.Figure 58.30 Removing Brake Disc
to Hub Bolts
4. Pull brake disc from wheel hub. Do not drive if off.
Install in reverse sequence, paying attention to the
following:
5. Prior to installation of the brake disc, ensure that
the contacting surface of brake disc to wheel hub is
free of burrs, dirt and high spots. If necessary,
remove high spots and check disc for flatness on a
surface plate. Carefully remove burrs with a scraper
or file.
6. Also check contacting surface of wheel hub to
brake disc to make sure it is in good condition. The
same applies to brake disc aligning shoulder on
wheel hub. See Figure
5B-315831
Figure
5B-31 Brake Disc to Hub Contact Surface

DISC BRAKES5B- 19
CAUTION:
Fasteners in Steps 7 and 9 are important
attachingparts in that they cooId affect theperfom-
ante of vital components and systems, and/or couJd
resuJt in major repair expense. They must be re-
placed with one of the same part number or with an
equivaJent part if repJacement becomes necessary.
Do not use a replacement part
or Jesser quaJity or
substitute design. Torque
vaJues must be used as
specified during
reassembJy to assure proper reten-
tion of these parts.7. Install brake disc on wheel hub and torque attach-
ing bolts to 36
Ib.ft. If old brake disc is reused, pay
attention to locator marks on brake disc and wheel
hub.8. Prior to installing brake disc and hub assembly to
steering knuckle, check lubrication of both roller
bearings and quantity of grease in cavity of wheel
hub. If necessary, repack front wheel bearings.
9. Adjust front wheel bearing clearance and tighten
brake caliper to steering knuckle, attaching bolts to
a torque of 72
lb.ft. Prior to installing brake caliper
to steering knuckle, ensure that all contacting sur-
faces are free of dirt and burrs. Also make sure that
the friction pads are not damaged when sliding the
brake caliper onto brake disc.
10. Install wheel assembly, remove supports and
lower front of car.
REMOVING AND INSTALLING
BRAKE DISC SHIELD
Removal
1. Remove brake disc.
2. Remove disc shield from steering knuckle by
removing one Phillips head screw on the outside and
on the inside, the lower steering arm and disc shield
to steering knuckle bolt. Remove paper gaskets from
steering knuckle. See Figure
5B-32.Installation
1. Prior to placing new paper gasket between brake
disc shield and steering knuckle, lightly coat both
surfaces of paper gasket with chassis lubricant.
2. Install disc and tighten disc shield and steering
arm to steering knuckle bolt to a torque of 47
lb.ft.CAUTION:
This steen;Og arm and steering knuckJe to
backing plate
fisteneris an important attachingpart
in that it
couJd at&t the performance of viral com-
ponents and systems, and/or
couJd resuJt in major
repair expense. It must be replaced with one of theFigure 58-32 Brake Disc Shield Attached
to SteeringKnuckle
same part number or with an equivalent part, if re-
pJacement becomes necessary. Do not use a rep/ace-
merit part of Jesser quaJity or substitute design.
Torque values must be used as specitied during reas-
sembly to assure proper retention of this part.3. Replace one Phillips head screw on outside of disc.
See Figure
5B-32.DISASSEMBLY AND ASSEMBLY
OF BRAKE CALIPER
1. Remove brake pipe from brake caliper. If both
calipers have to be repaired, it is advisable to mark
them with “L” or “R” on removal to avoid errors
when installing parts, such as pistons, etc. The brake
caliper halves must not be disassembled during re-
pair work. All work, such as pressing out pistons,
replacing seals in brake caliper, is carried out with
the two caliper halves bolted together.
2. Pry clamp rings from rubber seals, using a screw-
driver (Figure
5B-26) and remove rubber seals.
3. Remove piston first from caliper rim half (Figure
5B-33), and then out of the caliper mounting half
(Figure
5B-34) of the brake caliper, using mounting
clamp J-22429. To be able to force the piston out of
the caliper rim half, block the piston in the caliper
mounting half with mounting clamp J-22429 as
shown in Figure
5B-33. To force the piston out of the
caliper mounting half, place the mounting clamp on
caliper rim half, as shown in Figure
5B-34, and
tighten wing nut so that the rubber plate seals off the
caliper rim half bore. Then connect compressed air
hose to brake line connection in the caliper mounting

DRUM BRAKES5C- 23
Parking Brake Control System
The hand-operated parking brake lever is mounted
between the front seats on the propeller shaft tunnel.
A paw1 is riveted into the parking brake lever and is
actuated by a control rod provided with a spring
loaded push button. When the parking brake is ap-
plied, the parking brake lever is locked by the
paw1which engages the teeth on a stop plate. The parking
brake is disengaged by pressing the spring loaded
push button. See Figure
5C-41.
SPRING LOADED,-PUSH BUTTON
BRAKE LEVER
s\., \\,Figure
5C-4 1 Parking Brake Lever (Opel 1900 and
Manta)The GT arrangement of the parking brake is, with
the exception of the additional transmittal lever at
the floor panel, identical with that of the Opel mod-
els. The transmittal lever is attached to the propshaft
tunnel by means of a mounting support. See Figure
5C-42.The parking brake lever is connected with the front
parking brake pull rod. By means of an equalizer, the
front pull rod is connected to the forward portion of
a center cable. The center cable is routed rearward
through retaining guides and attaches at either end
to the lower end of a parking brake lever. See Figure
5C-43. The parking brake levers and struts actuate
the rear wheel brakes.
Service Brake Control System
-Standard Brakes
The service brake control system is a pedal operated
hydraulic system which applies the brakes at all four
wheels with equal pedal pressure. The hydraulic sys-
tem consists of a master cylinder (and attached trans-
parent fluid reservoir) connected by pipes and
1.PUSH BUTTON
2.THRUST SPRING
3.WASHER
4. PAWL CONTRO ROD
5. PARKING BRAKE LEVER
6.RIVET
7. HEX. HEAD BOLT
8.TOOTHED SEGMENT
9. PAWL WITH TWO TEETH
10.RUBBER CAP
11.THRUST ROD
12.PULL ROD
13.TRANSMITTAL LEVER
14.MOUNTING SUPPORT
15.BOLT
16. PARKING BRAKE CABLE
17. RETURN SPRING
sea2Figure 5C-42 Parking Brake Lever
(GT)flexible hoses to a wheel cylinder mounted between
the brake shoes at each rear wheel.
A mechanically-operated stop light switch is
mounted on a bracket just forward of the brake pedal
on the GT and just rearward of the brake pedal on
the Opel 1900 and Manta. With brake pedal released,
the switch plunger is fully depressed against the
switch actuating lever. See Figures
5C-45 and 5C-46.Any time the stop light switch fails, the stop lights
will stay on at all times.