Shifting
Shifting is the third domain of the Louisiana CDL General Knowledge exam. It tests whether you can select and change gears to keep the engine in its power band, control speed on grades, and avoid practices that damage the transmission or reduce control.
Manual transmission basics
Use double clutching: press the clutch, shift to neutral, release the clutch, press it again, and shift to the next gear. Progressive shifting-using only the rpm needed to reach the next gear-saves fuel and reduces wear. Do not coast in neutral; you lose engine braking and acceleration control. Do not ride the clutch or hold the pedal down at a stop.
Grades and speed control
Before a downgrade, slow down and select a lower gear while still on level ground. Use engine braking and stab braking as needed rather than riding the brakes, which can fade. On upgrades, downshift before the engine lugs; waiting until the truck is already struggling may force a missed shift.
Worked example
A loaded tractor-trailer approaches a long 6 percent downgrade at 55 mph. The driver downshifts to a gear that will hold about 35 mph before the crest, then uses brief brake applications to control speed. The reasoning: selecting the gear early keeps the engine in its braking range and prevents overheating the service brakes.
Traps
Coasting to save fuel, skipping gears in a way that overspeeds the engine, riding the clutch at lights, and shifting while crossing railroad tracks or in the middle of a turn all cost marks.