GMC 4000 Series Service Manual page 201

Sec. 5A
Page 194
HYDRAULIC BRAKES
cracked, or weakened, replace with new springs.
5. Inspect threads on adjusting screws and in
adjusting wheels for wear or damage. Replace as
necessary.
6. 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.
BRAKE SHOE INSTALLATION
1. Install adjusting screw s and wheels in
anchor supports dry; use no lubricant. Insert each
adjusting wheel in slot in anchor support, insert
threaded end of adjusting screw in anchor support,
then turn adjusting wheel to thread adjusting screw
into anchor support. Insert anchor pins into holes
in anchor supports, with slots in pins facing slots
in supports.
1 Hold-Down Pin
Spring Lock
2 Hold-Down Pin
3 Adjusting Screw
4 Adjusting Lever
5 Adjusting Lever Pin
6 Hold-Down Spring Cup
7 Lever Override
Spring
8 Brake Shoe and
Lining
9 Adjusting Lever
Pivot
10 Adjusting Lever Cam 22 Adjusting Lever
11 Adjusting Lever Bolt
12 Wheel Cylinder
Shield
Figure 3 6 — Twin-Action Rear Brake
Assem bly (Automatic Adjuster)
G M C S E R V I C E M A N U A L
13 Wheel Cylinder
14 Brake Shoe Return
Spring
15 Brake Shoe Anchor
16 Lever Return Spring
17 Adjusting Lever Pin
Sleeve
18 Hold-Down Spring
19 Brake Backing Plate
20 Hold-Down Pin
Retainer
21 Hold-Down Pin
Spring
Link
T-2698
2. Install brake shoes with cut-away end of
shoe web next to adjusting screw and with ends of
shoes engaging slots in wheel cylinder push rods
and anchor pins. Install flat washer and nut on each
brake shoe guide bolt. Tighten nuts finger-tight,
then back off nuts only far enough to allow move­
ment of shoes without binding.
3. Install brake shoe return springs, hooking
one end of each spring in brake shoe web, then
hook other end over anchor pins with special brake
spring tool (J-8049).
4. Remove wheel cylinder clamps.
5. Install hub and brake drum assembly as
directed in "REAR HUBS AND BEARINGS" (SEC.
4C) of this manual.
6. Adjust brakes as directed under "Brake
Adjustments."
TW IN-ACTION TYPE REAR BRAKE
(Refer to Figure 36)
BRAKE SHOE REMOVAL
1. Raise the vehicle and place on jack stands.
2. Remove brake drums.
NOTE: If brake drums are worn severely, it
may be necessary to retract the adjusting screw s.
3. Using Tool (J-22348), remove the brake
shoe pull-back springs (fig. 37).
NOTE: Since wheel cylinder piston stops are
incorporated in the anchor brackets, it is not nec­
essary to install wheel cylinder clamps when the
brake shoes are removed. However, the brake
pedal must not be depressed while the drums are
removed.
4. Loosen the adjusting lever cam cap screw
and while holding the star wheel end of the adjust­
ing lever past the star wheel, remove the cap screw
and cam.
Figure 3 7 — Re m oving Pull Back Sp rings