Shifting Gears
What this domain tests
Shifting Gears tests manual transmission control in a CMV: progressive shifting, clutch use, downshifting before grades, and avoiding coasting. The exam wants smooth gear changes that keep the engine in its power band and the vehicle under control.
Core rules
- Use progressive shifting: shift up at the lowest rpm that maintains power, saving fuel and wear.
- Do not coast in neutral; you lose engine braking and the ability to accelerate out of danger.
- Downshift before a downgrade, while speed is still low enough to match the lower gear.
- Use the clutch properly and avoid riding it; do not slip the clutch to hold on a hill.
- If rpm climbs on a grade, brake and downshift rather than letting the engine over-rev.
Worked example
A loaded tractor-trailer approaches a long downgrade at 55 mph. The driver waits until the top of the grade, then tries to downshift; the lower gear would over-rev the engine, so the shift is refused. Correct technique: slow before the crest, select a lower gear, and use engine braking with intermittent brake applications. The reasoning: a lower gear must be matched to a safe road speed before the descent begins.
Traps
Coasting downhill in neutral; skipping gears under load; lugging the engine; and holding the clutch halfway in heavy traffic.