Regional Haul Model Operator's Manual - Peterbilt Motors Company

DESCENDING A GRADE
ure or damage to the clutch and transmission and
overloads the brake system.
Coasting with the transmission in neutral also prevents
proper transmission component lubrication. During coasting
the transmission is driven by the rear wheels, and the
countershaft gear (which lubricates the transmission components
by oil splash) will only be turning at idle speed.
Descending a Grade
WARNING! Do not hold the brake pedal down
too long or too often while going down a steep
or long grade. This could cause the brakes to
overheat and reduce their effectiveness. As a
result, the vehicle will not slow down at the
usual rate. To reduce the risk of an accident
which could cause death or personal injury,
before going down a steep or long grade, reduce
speed and shift the transmission into a lower
gear to help control your vehicle speed. Failure
to follow procedures for proper downhill operation
could result in loss of vehicle control.
STARTING AND OPERATING THE VEHICLE
Engine Overspeed
CAUTION: To avoid engine damage, do not let
the engine rpm go beyond the maximum governed
rpm—valve damage could result if overspeed
conditions occur.
NOTE: Often these recommendations are secondary
to maintaining an adequate and safe
speed relative to the surrounding traffic and road
conditions.
Operate the engine within the optimum engine rpm range
and do not allow the rpm's to exceed the maximum governed
speed. See your Engine Operation and Maintenance
manual for information regarding engine rpm.
When the engine is used as a brake to control vehicle
speed (e.g., while driving down a grade), do not allow the
engine rpm to exceed maximum governed speed.
Under normal load and road conditions operate the
engine in the lower end of the range.
Use of Tachometer
The tachometer is an instrument that aids in obtaining the
best performance of the engine and manual transmission,
serving as a guide for shifting gears.
– 128 – Y53-6033 Regional Haul (R05/10)