PART 8: MAINTENANCE AND SERVICE
PB1319 (CAT. NO. 5296 ) —129— 22-01691 (R02/02)
If you have manual slack adjusters:
• Adjust the slack adjuster until the brake is tight.
• Then back off two or three clicks until the shoes are just free. You
can determine this by spinning the wheel or tapping on the drum
and listening for a clear ringing sound.
Normal pushrod travel is about 1 to 1 3/8 inch front and rear after
brakes have been properly adjusted.
Correct Pushrod Travel
If you have automatic slack adjusters: Constant manual adjustment of
automatic slack adjusters can shorten the life of your internal clutch.
If proper stroke cannot be maintained, replace the slack adjuster.
Operational Checks of Automatic Slack Adjusters
• Measure brake chamber stroke with the spring brake released and
the air pressure at 100 psi (690 kPa) minimum. Correctly installed
and functioning auto slack will produce the following strokes:
Type 36 chamber (rear brakes) should have a 1 1/2 inch to 2 1/4
inch (38 mm to 57 mm) stroke.
Type 30 chamber (rear brakes) should have a 1 1/2 inch to 2 inch
(38 mm to 51 mm) stroke.
CAUTION: The brake adjuster alone does not ensure
proper brake operation. Inspect all brake components. All
brake components work together and must be checked
periodically to ensure the brake system works properly.
See the Peterbilt Master Maintenance Manual for more
information on brake maintenance.
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