GMC 4000 Series Service Manual page 170

BRAKE ADJUSTMENT MODEL CHART
FRONT BRAKES
Type "FA"
Type "F"
(Manual) (Automatic)
S6500
L4000 Series
6500 Series
(exc. "S")
REAR BRAKES
Type "FR-3A"
Type "FR-3"
(Automatic)
(Manual)
S6500
6500 Series
(exc. "S")
MANUAL ADJUSTMENT
All manual brake adjustments to compensate
for normal lining wear can be made without re­
moving wheels and brake drums. Adjustment points
are accessible through openings in brake backing
plate or are external type.
FRONT SH O E
A D JU ST IN G STUD
W HEEL CYLINDER
BOLT
BLEEDER
VALVE
COPPER
G A SK E T S
C O N N E C T O R
TUBE
REAR SH O E
A D JU ST IN G STUD
Figure 2 — Type "F" Brake Adjustm ent
G M C S E R V I C E M A N U A L
justed before attempting to adjust brake shoes.
Refer to "HUBS AND BEARINGS" (SEC. 3D for
FRONT and SEC. 4C for REAR).
Duo-Servo
(Automatic)
(Type "F") are illustrated in figure 2. Adjustment
4500 Series
points for rear brakes (Type "FR-3") are shown
5500 Series
in figure 3.
Type "F" (Fig. 2)
Twin-Action clear floor- Place wrench on one adjusting cam
(Automatic) stud to adjust
L4000 Series of forward wheel rotation to decrease lining-to-
4500 Series drum clearance. Reduce clearance until brake
drag is felt as wheel is turned in forward direction
5500 Series
by hand.
until brake drag is relieved, then move wrench an
additional 7 to 10 degrees to provide running clear­
ance. (7 to 10 degrees is equal to 1 to 1/ inches
of travel at end of an 8-inch wrench.)
stud and adjust second shoe by repeating Steps 1
and 2.
CYLINDER BOLTS
HYDRAULIC BRAKES
NOTE: Wheel bearings must be properly ad­
Brake shoe adjustment points for front brakes
1. Jack up front end of vehicle until wheels
shoe. Rotate wrench in direction
2. Move wrench slightly in opposite direction
3. Place wrench on opposite adjusting cam
WHEEL
BLEEDER VALVE
REAR AXLE
BRAKE LINE
Figure 3 — Type " F R -3 " Brake Adjustm ent
Sec. 5A
Page 163
ADJUSTIN G
TOOL
C O N N EC T O R
TUBE