governed engine speed in the lower gears except in a peak load situation such as starting up a grade.
When driving conditions permit, maintain the desired road speed in a gear that permits running the engine
preferably 15 to 20 percent below governed speed to allow engine to accelerate to or to maintain governed RPM
when applying full throttle. In this cruise range, the engine affords better fuel economy than at higher speeds.
OPERATING ON GRADES
The biggest task when climbing a grade generally will be maintaining a reasonable rate of speed. When
possible, pre-plan the climb and probable shift requirements according to traffic conditions and grade to be
climbed. When approaching a hill, gradually move the throttle all the way down if necessary to maintain governed
RPM and remain at full throttle as the vehicle starts up the grade. If there is sufficient power to maintain
satisfactory road speed without engine laboring, remain in that gear for the entire grade. Whenever a grade
proves too great for the gear that you are in and the engine begins to labor, ease off on throttle as necessary and
allow speed to drop off to the next lower shift point before downshifting to the next gear. Speed usually drops off
quickly while shifting so shift should be made rapidly. Additional downshifting should be performed in the same
way, as necessary. By riding each gear down to the next shift point, you will get over your grades in the best
possible time with minimum shifts.
On downhill operation, the engine provides most efficient braking when run at or near top RPM in the
operating range BUT REMEMBER the governor has no control over the engine speed when it is being pushed by
a heavy vehicle. When the engine exceeds the rated governed RPM while descending a grade or downshifting at
the high end of the operating range, engine overspeed can result in serious damage. On downhill operation, use
the vehicle brakes and gears in combination to keep vehicle speed under control and engine below rated
governed RPM.
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