Regional Haul Model Operator's Manual - Peterbilt Motors Company
Regional Haul Model Operator's Manual - Peterbilt Motors Company
Regional Haul Model Operator's Manual - Peterbilt Motors Company
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OPERATING AUTOMATIC TRANSMISSIONS<br />
Brake Operation<br />
WARNING! Do not drive through water deep<br />
enough to wet brake components, as it may<br />
cause the brakes to work less efficiently than<br />
normal. The vehicle's stopping distance may<br />
be longer than expected, and the vehicle may<br />
pull to the left or right when brakes are<br />
applied, which could contribute to an accident<br />
that could cause death or personal injury.<br />
If you think your brakes have become wet, check the rear<br />
and both sides of the vehicle for clear traffic, then gently<br />
apply the brakes, releasing and gently reapplying until the<br />
brakes dry out—restoring normal operation. Always check<br />
your brakes after driving through deep water to help<br />
reduce the possibility of personal injury or an accident.<br />
Front Brake System<br />
When the brake pedal is depressed, the front circuit portion<br />
of the treadle valve delivers air from the front service<br />
reservoir to the front axle brake chambers via a quickrelease<br />
valve.<br />
STARTING AND OPERATING THE VEHICLE<br />
Simultaneously (on full truck configurations), air is also<br />
supplied to the modulating valve control port. In the event<br />
of a rear service circuit failure, the modulating valve will<br />
exhaust air from the spring brake chambers, applying the<br />
spring brakes in proportion to the front circuit application.<br />
Rear Brake System<br />
When the brake pedal is depressed, the rear circuit portion<br />
of the treadle valve delivers air from the rear service<br />
reservoir to the service brake relay valve control port. The<br />
relay valve then delivers air directly from the rear service<br />
reservoir to the rear brake chambers in proportion to the<br />
treadle pressure.<br />
On tractors without ABS, the relay valve is part of the BP-<br />
R1 brake valve, which automatically proportions the drive<br />
axle brake application pressure when driving bobtail (without<br />
a trailer connected). The proportioning BP-R1 brake<br />
valve allows full use of the steer axle (front) brakes and<br />
reduces the chance that the drive axle brakes will lockup.<br />
The bobtail brake proportioning system is automatically<br />
turned off when a trailer is connected.<br />
– 102 – Y53-6033 <strong>Regional</strong> <strong>Haul</strong> (R05/10)