Chevrolet Light Duty Truck 1973, Service Manual

Page: 289 / 979

BRAKES 5 -2 3
parking brake is mounted on the propeller shaft) serve a
dual purpose in that they are utilized both as a
hydraulically operated service brake and also as a
mechanically operated parking brake. In view of this
dual purpose, the service brake must be properly
adjusted as a base for parking brake adjustment;
conversely the parking brake must be properly adjusted
for the service brake to function as intended.
Inspection
If complete release of the parking brake is not obtained,
unless it is forcibly returned to its released position, or if
application effort is high, check parking brake assembly
for free operation. If operation is sticky or a bind is
experienced, correct as follows:
1. Clean and lubricate brake cables and equalizer with
Delco Brake Lube #5450032 (or equivalent).
2. Inspect brake assembly for straightness and
alignment (replace if necessary).
3. Clean and lubricate parking brake assembly with
Delco Brake Lube #5450032 (or equivalent).
4. Checking routing of cables for kinks or binding.
Adjustment—Foot Pedal Type
NOTE: Before adjusting parking brake,
check service brake condition and
adjustment.
1. Raise vehicle on hoist.
2. Apply parking brake 1 notch from fully released
position.
3. Loosen equalizer check nut and tighten the
adjusting nut until a moderate drag is felt when the
rear wheels are rotated forward.
4. Tighten the check nut to specifications.
CAU TIO N :
See Caution on Page 1 of this
section.
5. Fully release parking brake and rotate the rear
wheels. No drag should be present.
6
. Remove vehicle from hoist.
Adjustment—Orscheln Lever Type
1. Turn adjusting knob on parking brake lever
counterclockwise to stop.
2. Apply parking brake.
3. Raise vehicle on a hoist.
4. Loosen lock nut at intermediate cable equalizer and
adjust front nut to give light drag at rear wheels.
Tighten the check nut to specifications.
CAUTIO N:
See Caution on Page 1 of this
section.
5. Readjust parking brake lever knob to give a definite
snap-over-center feel.
6
. Fully release parking brake and rotate rear wheels.
No drag should be present.
7. Remove vehicle from hoist.
PARKING BRAKE (PROPELLER S H A FT)-
INTERNAL EXPANDING
Adjustment—Drum On
1. Jack up at least one rear wheel. Block wheels and
release hand brake.
2. Remove cotter pin and clevis pin connecting pull
rod and relay lever. This will assure freedom for
full shoe release.
CAUTIO N:
It may be necessary to knock out
lanced area in brake drum with punch and
hammer to gain entry into adjusting screw
through brake drum. Be sure all metal has been
removed from parking brake compartment.
3. Rotate brake drum to bring one of access holes into
line with adjusting screw at bottom of shoes.
4. Expand shoes by rotating adjusting screws with
screwdriver inserted through hole in drum. Move
outer end of screwdriver away from drive shaft.
Continue adjustment until shoes are tight against
drum and drum cannot be rotated by hand. Back
off adjustment ten notches and check drum for free
rotation.
5. Place parking brake lever in fully released position.
Take up slack in brake linkage by pulling back on
cable just enough to overcome spring tension.
Adjust clevis of pull rod or front cable to line up
with hole in relay levers.
a. Insert clevis pin and cotter pin, then tighten
clevis locknut.
b. Install a new
metal
hole cover in drum to
prevent contamination of brake.
c. Lower rear wheels. Remove jack and wheel
blocks.
CAUTIO N:
See "Caution" on Page 1 of this
section.
Adjustment—Drum Off
1. With parking brake drum off, use special Tool
J-21177 or J-22364, Drum to Brake Shoe Clearance
Gauge, to check diameter of drum clearance
surface.
2. Turn the tool to the opposite side and fit over brake
shoes by turning the star wheel until the gauge just
slides over the linings.
3. Rotate the gauge around the brake shoe lining
surface to insure proper clearance.
4. Install propeller shaft flange at mainshaft as
outlined in transmission section.
5. Lower rear wheels. Remove jack and wheel blocks.
LIGHT DUTY TRUCK SERVICE MANUAL