GMC 4000 Series Service Manual page 220

1 Adjusting Worm Shaft
2 Lubrication Hole Plug
3 Clevis Pin
4 Slack Adjuster
5 Adjusting Clevis
Mounting Bracket
6
Figure 8 — Brake Cham ber and Slack
Adjuster Installed (Front)
brakes and make sure all slack adjusters return
to released position freely without binding.
With brakes released, make sure the angle
formed by slack adjuster arm and brake chamber
push rod is greater than 90 degrees. All slack
adjusters should be set at the same angle. With
brakes applied, make sure the angle formed by the
slack adjuster arm and brake chamber push rod is
still slightly greater than 90 degrees and that all
are at the same angle. If angle is less than 90 de­
grees with brakes applied, slack adjuster is going
"over center." Adjust brakes as previously des­
cribed under "Brake Adjustments."
SLACK ADJUSTER REPLACEMENT
(Refer to Figs. 8 and 9)
Removal
1. Remove clevis pin attaching brake chamber
push rod yoke to slack adjuster.
2. Remove lock ring or cotter pin and spacer
securing slack adjuster on camshaft. Slide slack
adjuster off end of shaft.
Installation
1. If a new slack adjuster is being installed,
make sure it is the same size and type as that
removed. Make sure spacing washer is in place on
camshaft. Slide slack adjuster onto camshaft and
G M C S E R V I C E M A N U A L
7 Brake Chamber
Air Brake Hose
8
9 Front Axle
10 Brake Camshaft
11 Snap Ring
1 Air Brake Hose
2 Brake Chamber
3 Mounting Bracket
4 Slack Adjuster
5 Rear Axle
Figure 9 —Brake Cham ber and Slack
Adjuster Installed (Rear)
attach with spacer and lock ring or cotter pin.
2. Connect brake chamber push rod yoke to
slack adjuster with clevis pin and cotter pin. Refer
to "Brake Chamber Installation" for adjustment of
brake chamber push rod.
3. Adjust brakes as directed under "Brake
Adjustments."
BRAKE CHAMBERS (STANDARD)
All service information in the following par­
agraphs refers only to standard chambers. Cham­
bers used on rear brakes only on 6500 Series are
covered under the separate heading of "Stopmaster
Brakes." "Stopmaster" and "Fail-Safe" brakes are
also available on all Series 5500 as optional equip­
ment. Chambers used as optional equipment for air
operated emergency and parking brakes are cover­
ed under separate headings of "DD3 Brake Actuator
System" or "AnchorlokBrake Chambers." Standard
chambers on rear brakes of Series 4000 tilt cab
models, all Series 5500 models, and for front
brakes are covered here.
An air brake chamber is used at each wheel
to convert the energy of compressed air into the
mechanical force and motion required to apply the
brakes. The yoke on the brake chamber push rod
connects to a slack adjuster which is mounted on
the brake camshaft. Push rod opening and four
Sec. 5B
Page 213
AIR BRAKES
Snap Ring
6
7 Brake Camshaft
Lubrication Hole Plug
8
9 Clevis pin
10 Adjusting Clevis
1.2194