GMC 4000 Series Service Manual page 247

Sec. 5B
Page 240
AIR BRAKES
Figure 3 2 — Staking Air Cham ber Lockwasher
spanner nut against lock washer and the spider
housing. Using a punch, drive edge of lock washer
into notches provided in spider housing and span­
ner nut (see fig. 32).
BRAKE SHOE A N D LININGS
BRAKE SHOE REMOVAL (Refer to Fig. 33)
1. Jack up rear of vehicle and remove wheels.
2. Remove hub and brake drum assembly.
Refer to "Rear Suspension" under "REAR HUBS
AND BEARINGS" (Sec. 4C) of this manual.
3. Remove brake shoe return springs.
4. Lift brake shoe web out of shoe hold-down
clip and out of notches in anchor and adjusting
plungers. NOTE: Mark adjusting end of brake
shoes to insure correct reassem bly.
SHOE RELINING
Each brake shoe consists of a shoe table with
a single web welded in place. A two-piece molded
lining is riveted to each shoe. Lining should be
replaced before wear exposes the rivet heads and,
causes damage to brake drums. Both linings on
each shoe are identical and can be installed at
either end. New linings must be securely riveted
G M C S E R V I C E M A N U A L
to shoe with correct size rivets, and rivets must
be properly upset. Maximum braking efficiency
can be obtained immediately if linings are trued-
up with a lining grinder so they are properly cen­
tralized in relation to center of hub.
BRAKE SHOE INSTALLATION
(Refer to Fig. 33)
clips with ends engaging slotted end of anchor
plungers and slotted end of adjusting bolt.
4-inch radius on the adjusting end and a 3-inch
radius on the anchor end. When installing shoes
on brake assembly, make certain the end marked
as suggested in "NOTE" of step 4 of "Removal"
is mounted in adjusting plunger.
certain hold-down clip applies pressure to shoe
web to avoid cocked shoes.
BRAKE ACTUATION COMPONENTS
removing spider from axle. Trouble diagnosis
might indicate faulty internal parts which would
not necessitate brake chamber disassembly or new
brake lining. Actuation components should be in­
spected for faulty or unacceptable conditions.
see procedures under that subject on a previous
page of this section. The following procedures
cover the anchor end components and other ac­
tuation components.
REMOVAL (Refer to Fig. 33)
ures covering standard and/or "Fail-Safe" cham­
ber service.
pressure housing from brake spider. This leaves
wedge, roller and spring assembly exposed.
from actuation housing by pulling straight out.
covering this operation.
described in applicable procedures.
DISASSEMBLY OF WEDGE ASSEMBLY
(Refer to Figs. 33 and 34)
washer from wedge assembly.
from roller retaining cage.
1. Position brake shoe webs inside hold-down
NOTE: Brake shoes are constructed with a
2. Install brake shoe return springs. Make
Actuation components can be serviced without
For service of automatic adjuster components
1. Remove brake chambers. Refer to proced­
2. Loosen spanner nut, then unscrew non­
3. Remove wedge, roller and spring assembly
4. Remove brake shoes. Refer to procedure
5. Remove plunger guides and washers.
6. Pry plunger seal from spider housing.
7. Remove anchor plunger.
8. Remove automatic adjuster components as
1. Remove cotter pin and wedge return spring
2. Slide wedge spring off wedge.
3. Remove wedge retainer washer and rollers