Chevrolet 10 Series 1968, Service Manual

Page: 263 / 713

BRAKES 5-30
F ig . 56—W agner Type “ F R -3 ” Rear Brakes
1. Wheel C ylin d e r Heat Shield
2. Upper Wheel C y lin d e r
3. A nchor Pin
4. Return Spring (Short)
5. G u id e Washer
6. G u id e Bolt
7. G u id e Bolt N ut Lock Wire
8. Brake Shoe and Lining
Assembly
9. Return Spring (Long)
10. A djusting Wheel Lock Spring
11. Adjusting Wheel
12. Lower Wheel C ylin d e r
13. Backing Plate
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5.
9.
10
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11
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Clean all dirt out of brake drum. Inspect drum for
roughness, scoring, or out-of-round.
Recondition or replace drum as necessary. Inspect
brake flange plate for oil leakage past axle shaft oil
seal. Install new seals if necessary.
Clean all dirt from brake components.
Inspect wheel bearings and oil seals as directed in
Section 3.
Inspect b r a k e shoe return springs. If broken,
cracked, or weakened, replace with new springs.
To disassemble the automatic adjuster from shoe,
unhook wedge actuating coil spring from wedge. Un­
hook lever actuating spring from shoe web, work
spring coil off of lever pivot pin and slide spring
“ U” hook off of contact plug-lever pin. Pull adjuster
lever from opposite side of shoe web, contact plug
through shoe table and lift off wedge washer, wedge
and wedge guide.
To remove wheel cylinder, remove connecting tubing,
anchor bolt and mounting screws.
SHOE RELINE - A 3/4 inch hole is required for the
contact plug. If lining is not pre-drilled, locate the
hole by making a paper template of the shoe table.
Cut hole with a hole saw and de-burr the edges. If
lining is to be surface ground, an assembled contact
plug may be ground even with lining by blocking
automatic adjuster in fully extended position. Grind
lining 0.020 to 0.030 inch less than standard drum
diameter to provide “ break in” clearance at lining
ends.
N OTE:
The Wagner Type “ F A ” front brakes
must be manually adjusted with drum on at all
initial installations as this type brake does not
automatically adjust initial clearance.
Installation (Fig. 58)
1. Install automatic adjuster, contact plug flush with
lining surface: Replace wedge guide on shoe web on
side away from mounting plate, serrations facing
away from shoe table. Lay wedge on web with serra­
tions against matching serrations on the wedge guide,
slot aligned on lever pivot pin hole. Insert contact
plug, from drum side of shoe, guiding its shank
through the hole in the shoe table and over wedge
guide and wedge. Insert adjuster lever pins through
shoe web from opposite side, guiding the actuating
(center) pin into the mating hole of the contact plug
shank. Place wedge washer over shoulder of pivot
pin. Slide “ U” hook of adjuster spring on pin over
contact plug shank. Attach end of wedge actuating
spring to this hook, then install coil of adjuster
torsion spring over the pivot pin and pull the spring
hook over the edge of web. Connect wedge actuating
spring on raised hook on the wedge “ fork.” Fully
retract the wedge against the lever pivot pin, press­
ing upon the contact plug to permit this movement.
If plug now protrudes more than 0.005-inch above
lining, clamp shoe in vise so that vise jaws bear
against the adjuster lever and dress down the plug.
This can be done with a file, taking care not to create
a “ flat spot” on the lining. (Alternately, plug may be
ground with lining by blocking adjuster lever in ex­
tended position.) If fully extended plug is more than
0.005-inch below lining surface, replace with new
Plug.
2. Make sure that brake backing plate, wheel cylinder
anchor bolts and cylinder mounting screws are
torqued to specifications.
3. Install shoes on hold-downs, locating each retracting
spring so that its long shank is hooked at the anchor
end of the shoe.
4. Install flat washers and hold down C-washers.
5. Install brake shoe return springs with Tool J-8049.
6. Adjust brakes—Initial manual lining adjustment.
a. Back off manual adjustment cams.
b. Center each shoe, before installing drum, by
sliding shoe up or down in its anchor slot until
the leading and trailing edges of the linings are
equal distance from the inner curl of the brake
mounting plate.
c. Install hub and brake drums as directed in Section
3.
d. At one manual shoe adjuster stud, rotate adjuster
cam stud in the direction of forward drum rota­
tion, tightening the adjustment until the shoe
drags on drum. Back off the adjuster cam stud
while rotating drum forward, until drag just is
relieved.
e. Adjust the second manual shoe adjuster stud in
the same manner, forward to tighten and reverse
to relieve drag.
7. Lower vehicle and rebleed if necessary.
CHEVROLET TRUCK SERVICE MANUAL