4-9.6
Automatic Slack Adjusters
The trailers automatic slack adjusters provide
the means for routine brake adjustment to compen-
sate for lining wear. Inspect slack adjusters every
2,000 miles to assure correct operation.
a. Operational Check (See Figure 4-13)
1.
Block wheels to prevent vehicle from
rolling.
2.
Check that the push rod is fully retracted,
apply air to release spring brake.
3.
Turn adjustment hex counterclockwise to
create an excessive clearance condition. (A
ratcheting sound will occur.)
4.
Make a full service brake application. On
release, allow sufficient time for brake to
fully retract. During the brake release,
observe rotation of the adjustment hex
(attach a wrench on the hex to make this
movement easier to see). This rotation
indicates that an excessive clearance
condition has been determined by the slack
adjuster, and it is making an adjustment to
compensate. On each subsequent brake
release the amount of adjustment and push
rod travel will be reduced until the desired
clearance is achieved
5.
The push rod stroke should be 1 1/2" to 2"
with an 100 to 105 PSI service brake
application.
6.
Measure the movement of the push rod
from the completely released position to the
applied position by marking the push rod
where it exits the air chamber before and
after application.
7.
If the brakes have been running tight, the
slack adjuster should be checked.
WARNING
IF THE ADJUSTER APPEARS NOT TO
BE OPERATING, CHECK THE OTHER
BRAKE COMPONENTS FOR PROPER
FUNCTION AND ELIMINATE ANY BIND-
ING. RECHECK THE AUTOMATIC
SLACK ADJUSTER. IF THE ADJUSTER
IS NOT FUNCTIONING, THE UNIT
MUST BE REPLACED BECAUSE FAIL-
URE OF PROPER ADJUSTMENT
FUNCTION WILL RESULT IN LOSS OF
BRAKES.
b. Replacing Slack Adjuster
(
See Figure
CAUTION
THE INSTALLATION GUIDE MUST BE
USED WHEN INSTALLING OR REIN-
STALLING AUTOMATIC SLACK AD-
JUSTER. FAILURE TO DO SO MAY RE-
SULT IN IMPROPERLY ADJUSTED
BRAKES WHICH MAY CAUSE BRAKE
DAMAGE OR LEAD TO BRAKE FAIL-
URE.
1.
Chock wheels to prevent vehicle from
rolling. Release spring and service brake.
Air chamber push rod must be fully
released.
2.
To maintain a fully released parking brake,
a minimum of 90 psi reservoir pressure
must be maintained. If air pressure is not
available the spring brake must be
manually caged.
3.
Remove the existing slack adjuster and
clevis -
DO NOT REMOVE EXISTING JAM
NUT
.
4.
Install the new clevis (with 1/2" pin) onto
the push rod up to the jam nut -
DO NOT
TIGHTEN JAM NUT
.
4-17
Summary of Contents for 334C
Page 3: ...MODEL 334C CAR CARRIER OPERATOR S MANUAL PURCHASED FROM DATE ADDRESS PHONE NO SERIAL NO...
Page 8: ......
Page 24: ...3 12 Figure 3 7 Lining Up the Over the Cab Deck Figure 3 8 Loading the Over the Cab Deck...
Page 28: ...3 16 Figure 3 11 Loading the Lower Deck...
Page 32: ...3 20 Figure 3 13 Rear Impact Guard and Antilock Brake System...
Page 40: ...4 6 Figure 4 3 Model 334C Wiring Diagram...
Page 45: ...4 11 Figure 4 7 Checking Axle for Bend Figure 4 8 Examples of Camber...
Page 50: ...4 16 Figure 4 12 Axle and Brake Assembly...
Page 54: ...4 20 Figure 4 14 Outboard Mount Hub and Drum Figure 4 15 Inboard Mount Hub and Drum...
Page 59: ...4 25 Figure 4 19 Mounting Tires and Wheels Figure 4 20 Stud Tightening Sequence...
Page 70: ...NOTES 5 10...
