Medium Duty Operator's Manual - Peterbilt Motors Company

STARTING AND OPERATING THE VEHICLE
During Normal Driving
If you want to shift directly into any gear other than
first or reverse, depress the clutch pedal only far
enough to release the clutch. Pushing the clutch to
the floor applies the clutch brake and could cause gear
hang-up.
CAUTION: Be careful not to apply the clutch
brake while the vehicle is moving. The purpose
of the clutch brake is to stop the transmission
so that you can shift into a starting
gear without grinding gears. Applying the
clutch brake when the vehicle is moving
causes a braking effect on the drivetrain and
shortens the service life of the clutch brake.
Double Clutching
Whether you are upshifting or down shifting, it is best to
double clutch. Double clutching is easier on the transmission
and on the engine, helping your vehicle match engine
speed with driveline speed and achieving clash-free
shifts.
To double clutch:
OPERATING THE TRANSMISSION
1. Push the clutch pedal down to disengage the
clutch.
2. Move the gear shift lever to Neutral.
3. Release the pedal to engage the clutch. This lets you
control the rpm of the mainshaft gears, allowing you to
match the rpm of the mainshaft gears to those of the
output shaft.
• Upshifts: let the engine and gears slow down to the
rpm required for the next gear.
• Downshifts: press accelerator, increase engine and
gear speed to the rpm required in the lower gear.
4. Now quickly press the pedal to disengage the clutch
and move the gear shift lever to the next gear speed
position.
5. Release the pedal to engage the clutch.
More Transmission Tips
“Riding” the Clutch
The clutch is not a footrest. Do not drive with your foot
resting on the clutch pedal. It will allow your clutch to slip,
causing excessive heat and wear—damage could result.
Medium Duty (R05/09) Y53-6008A – 99 –