GMC 1976 ZEO 6083 Maintenance Manual page 220

Contents of this section are listed below :
SUBJECT PAGE NO .
General Information . . .... . ... . .... . . .. . . . .. . . ... . ... . . ... . . ... . ... . . .. . . ... . . .. . . . . . . . .... . ... . . ... . . .. . . ... . . ... . .... . ... .. .. . .. . .5-1
Brake System Trouble Diagnosis . . ... . .... .... . ... . . . .. . . .. . . . . . . . ... . ... . . ... . . ... . . .. . . . .. . . ... . .... . ... .. . .. . . .. . . .. . . . . . 5-4
On-Vehicle Servicing .. .... . . .. . . . ... . .... . ... . .... . ... . ... . . . .. . . .. . . . .. . . ... . ... . . ... . . ... . . .. .. . ... . .... . ... . . ... . . .. . . .. . . . .. . . 5-14
Component Removal . . .... . ... . .... . ... . . .. . . . .. . . ... . . .. . . . ... . ... . ... . . ... . . .. . . . . . . . ... . .::. . . .. . . . .. .. ... . . ... . .... . ... . ... . .. 5-17
Component Overhaul .... . ... . .... . . .. . . . .. . . ... . ... . . ... . . . .. . ... . . .. . . ... . . .. . . . .. . . .... . ... . . .. . . . ... . .... . ... . .... . ... . ... . .. 5-25
Major Component Inspection . . . .. . . . .. . . .... .... . ... . . . .. . . .. . . ... . . ... . ... . . ... . . ... . . .. . . . .. . . .... . ... . ... .. ... . . .. . . .. . . . 5-37
Component Installation .. . . .. . .. .. . . ... . . ... . .... .... . ... . . . ... . ... . . ... . .... .... . . .. . . . ... . .... . ... . . ... . . .. . . . .. . . ... . ... . . .. . . 5-40
Specifications ... . . .. . . . ... . .... . ... . .... . ... . . .. . . ... . . ... . . .. . . . . .. . . .. . . ... . . .. . . ... . . ... . . ... . . .. . . . .. . . .... .... . ... . . ... . . .. . . .. . . . 5-46
Torque Specifications .. .... . ... . . ... . . .. . . . ... . ... . .... . ... . . . .. . . .. . . . . . . . .. . . ... . . ... . . ... . . .. . . . .. . . .... .... . ... . .... . . .. . . . .. . . 5-46
Special Tools . ... . . ... . .... .... . . . .. . . ... . . ... . .... .... . ... . . . .. . . ... . . .. . . ... . .... . ... . . . .. . . . ... . .... . ... . . .. . . ... . . ... . . .. . . 5-46
CAUTION :
All brake system fasteners are important attaching parts in that they
could affect the performance of vital components and systems, and/or could
result
in
major repair expense. They must be replaced with one ofthe same part
number or with an equivalent part ifreplacement becomes necessary. Do not
use a replacement part oflesser quality or substitute design . Torque values must
be used as specified during reassembly to assure proper retention oftheseparts.
The vehicle is equipped with disc brakes on the
SELF-ADJUSTING BRAKE
front wheels, and has drum brakes on the rear
wheels. They are hydraulically powered by a split The vehicle is equipped with self-adjusting
hydraulic system . brakes . The self-adjusting brake mechanism consists
of an actuating link, adjuster lever, adjuster lever
return spring, override spring and override pivot. When the brake pedal is depressed, the piston in
the master cylinder forces fluid under pressure to a
wheel cylinder at each wheel, which in turn, pushes
the brake shoes against the brake drum. As the shoes
contact the drum, the friction between the shoes and
the rotating drum moves the primary shoe down-
ward against the adjusting screw which acts as a link
to transmit the force of the primary shoe to the lower
end of the secondary shoe . With the upper end of the
secondary shoe being held by the stationary anchor
pin, the secondary shoe is wedged against the drum .
This wedging action, due to frictional force impacts
the self-energizing action to the braking effort and
thereby decreases the effort required by the driver to
stop the vehicle.
SECTION 5
BRAKES
GENERAL INFORMATION
OPERATION (DRUM TYPE)
BRAKES
5- 1
The self-adjusting brake mechanism operates
only when the brakes are applied while the vehicle is
moving rearward and only when the secondary shoe
moves a predetermined distance toward the brake
drum .
As the vehicle moves rearward and the brakes are
applied, friction between the primary shoe and the
drum forces the primary shoe against the anchor pin.
Hydraulic pressure in the wheel cylinder forces the