PART 7: STARTING & OPERATING THE VEHICLE
PB1319 (CAT. NO. 5296 ) —93— 22-01691 (R02/02)
Descending a Grade
Engine Overspeed
• 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 perfor-
mance of the engine and manual transmission, serving as a guide for
shifting gears. Refer to the
Engine Operation and Maintenance man-
ual
for optimum engine rpm.
If the engine rpm moves beyond the maximum governed speed, indi-
cating an overspeed condition, apply the service brake or shift to a
higher gear to bring engine rpm within the optimum speed range.
• When driving downhill: shift to a lower gear, use the engine brake
(if so equipped), and use the service brake, keeping the engine
speed below 2,100 rpm.
When the engine speed reaches its maximum governed speed, the
injection pump governor cuts off fuel to the engine. However, the gov-
ernor has no control over the engine rpm when it is being driven by
the vehicle’s transmission, for example, on steep downgrades. Apply
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 effec-
tiveness. As a result, the vehicle will not slow down at the
usual rate. To reduce the risk of personal injury and/or an
accident, 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.
CAUTION: To avoid engine damage, do not let the engine
rpm go beyond the maximum governed rpm—valve dam-
age could result if overspeed conditions occur.
NOTE: Often these recommendations are secondary to main-
taining an adequate and safe speed relative to the surrounding
traffic and road conditions.
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