TRUCK SERVICE MANUAL
certain that it is in fully released position. To do this,
disconnect the push rod at the slack adjuster. If push
rod moves toward (release) the brake chamber, turn
the worm shaft and rotate the slack adjuster toward
the push rod until the clevis pin can be reinstalled.
2. Disengage locking sleeve on worm shaft or adjusting
screw by depressing the spring loaded sleeve with
open or box end wrench (Fig. 6).
Fig. 7 Brake Chamber and Slack Adjuster
force against the slack adjuster cannot be obtained.
Readjust push rod as follows:
1. Disconnect the slack adjuster and push rod. Do this
carefully because the slack adjuster may be turned
toward the brake chamber with considerable
Loosen the lock nut on the clevis and thread the
clevis onto the push rod toward the brake chamber,
for several turns.
3. Reconnect the slack adjuster and push rod with clevis
4. Make a full brake application and check the angle
between the slack adjuster and push rod. If it is not
greater than 90° with the brakes applied, repeat the
Fig. 6 Stack Adjuster Locking Sleeve on Adjusting Nut
adjustment until the angle is satisfactory. The
desirable situation is to bring the brake shoes
Turn the vehicle wheel and at the same time the
against the drum as the slack adjuster attains the
rotate adjusting screw until the brake shoes are tight
90° position, Fig. 7.
against the drum.
5. Once adjustment is correct, install the cotter pin and
4. Back off the adjusting .screw just enough to eliminate
tighten the clevis lock nut securely. Perform the
above adjustment at each wheel in turn.
Make and hold full brake application to fully seat
brake shoes against drum and note the angle
between the slack adjuster and the push rod. This
Friction surface of brake drum must be smooth, true and
angle must be greater than 900 as stated in "BRAKE
concentric. Make sure that the drum is not bulged,
bell-mouthed, scored, or eccentric. A bulged drum
results from overheating (Fig. 8). Braking surface is
If the foregoing adjustment or relining of the brake
reduced and uneven lining wear will result if this
shoes does not establish a greater angle than 900
condition is not corrected.
between the push rod and slack adjuster with brakes
applied, then maximum
Extreme pressures which, over a period of time will
create a bell-mouthed drum as