GMC 4000 Series Service Manual page 242

held in place by a lock ring at each end. A leather
seal is used between lock ring and shoe web at
outer end and between dust shield and shoe web at
inner end to retain lubricant and exclude dirt. Shoe
ends are not equipped with bushings; if shoes or
anchor pins become worn, parts must be replaced.
Refer to figure 26 for cross-sectional view.
At cam end of each shoe, a roller installed
between shoe webs on a roller pin makes the con­
tact between shoes and cam. Flats on end of roller
pin fit into notches in shoe webs. Tension of brake
shoe return spring holds shoe rollers firmly against
cam. Return spring pins are staked in 8 places so
that they will not slide out of shoe webs. No lubri­
cation is required at rollers or roller pins; parts
should be assembled clean and dry. Anchor pin
ends should be coated with S-17 Special Lubricant
or equivalent during installation.
A two-piece molded lining is riveted to each
shoe. Linings should be replaced before wear ex­
poses 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 to shoe with correct size rivets,
and rivets must be properly upset. Maximum brak­
ing efficiency can be obtained immediately if lin­
G M C S E R V I C E M A N U A L
Section A - A
Looking in Direction
of A rrow s
1 Brake Shoe
2 Brake Shoe Return
Spring
3 Cam (integral with
shaft)
4 Camshaft Seal
5 Camshaft Bushing
6 Brake Spider
7 Dust Shield
8 Camshaft and Brake
Chamber Bracket
Figure 2 5 — Rear Brake Assem bly
14 Anchor Pin
9 Camshaft
10 Snap Ring 15 Leather Seal
11 Spacers 16 Brake Shoe Roller
12 Slack Adjuster 17 Roller Pin
13 Lock Ring 18 Brake Shoe Lining
ings are trued-up with lining grinder so they are
properly centralized in relation to center of hub.
Whenever any part of the brake assembly has
been removed and replaced, adjust brakes as di­
rected under "Brake Adjustments."
Sec. 5B
Page 235
AIR BRAKES
T P M -7 6 3 0