GMC 4000 Series Service Manual page 199

______________________ G M C S E R V I C E M A N U A L
Page 192
HYDRAULIC BRAKES
Connector Tube
1
Spring Washer
2
Bolt
3
Flat Washer
4
Backing Plate
5
Bleeder Valve
6
Wheel Cylinder
7
Brake Shoe
8
9 Flat Washer
Anti-rattle
10
Washer
11 C-washer
12
Return Spring
13 Wedge Guide
CLEANING AND INSPECTION
1. Clean all dirt out of brake drum. Inspect
drum for roughness, scoring, or out-of-round.
Replace or recondition brake drum as necessary.
Refer to "Brake Drums" in this section.
2. Inspect bearings and oil seals as directed
in "FRONT HUBS AND BEARINGS" (SEC. 3D) in
this manual.
3. Check backing plate attaching bolts to make
sure they are tight. Clean all dirt off backing plate.
4. Inspect brake shoe return springs. If broken,
cracked, or weakened, replace with new springs.
5. Check cam and shoe guide stud and friction
spring on backing plate for corrosion or binding.
Cam stud should turn easily with an 8-inch wrench,
but should not be loose. If frozen, lubricate with
kerosene or penetrating oil and work free.
6. Check all automatic adjuster components
and replace any which are worn or damaged. Re­
place springs if broken, cracked, or weakened.
7. Check wheel cylinders as instructed under
"Wheel Cylinder Repair" in this section. Replace
with new cylinders if necessary.
8. Examine brake shoe linings for wear. Lin­
ings should be replaced if worn down close to rivet
heads. Refer to "Brake Shoe Relining" in this
section.
14 Contact Plug
15 W edge Spring
16 Torsion Spring
17 Retainer Washer
18 Wedge
19 Adjuster Lever
20 Brake Lining
21 Rivet
Figure 3 4 — Type "F A " Front Brake Components
ASSEMBLE AUTOMATIC ADJUSTER
(Refer to Figure 34)
1. Place the wedge guide on the shoe web (side
away from mounting plate) with the serrations
facing away from the shoe table.
2. Lay the wedge on the shoe with the serra­
tions against matching serrations on the wedge
guide. Align wedge slot with pivot pin hole.
3. Insert contact plug from drum side of shoe,
guiding its shank through the hole in the shoe table
and over the wedge guide and wedge.
4. Place adjuster lever on opposite side of
shoe web and insert pins through holes in shoe
web and mating hole in contact plug shank.
5. Place retainer washer over wedge pivot
pin.
6. Slide "U" hook of torsion spring on pin
over contact plug shank. Attach end of wedge spring
to this hook, then install coil of torsion spring over
the pivot pin and pull the spring hook over the edge
of shoe web.
7. Connect wedge spring oh raised hook on
the wedge "fork."
8. Fully retract the wedge against the lever
pivot pin, pressing on the contact plug to permit
this movement. If the plug now protrudes more
than 0.005" above lining, clamp shoe in vise jaws
bear against the adjuster lever and dress down the
T-4578