Examkin

Question

Difficulty: MediumUpshifting and Double Clutching

When accelerating a commercial motor vehicle equipped with an unsynchronized manual transmission, proper double-clutching is required to shift into a higher gear. In what chronological order should a driver execute the physical actions to complete a standard upshift once reaching the target shift point?

  1. 1Release the accelerator, depress the clutch pedal, and move the gearshift lever into neutral.
  2. 2Release the clutch pedal completely while keeping the transmission in neutral.
  3. 3Allow engine speed and transmission input shaft speed to drop to the RPM required for the higher gear.
  4. 4Depress the clutch pedal again and move the gearshift lever firmly into the higher gear.
  5. 5Release the clutch pedal smoothly while pressing the accelerator to continue accelerating.

Answer

The proper sequential order for double-clutch upshifting is: (1) Release accelerator, push clutch in, shift to neutral; (2) Release clutch pedal; (3) Allow engine and gears to slow down to the target RPM; (4) Push clutch pedal in and shift to the higher gear; (5) Release clutch pedal and press accelerator.
According to the official CDL manual, upshifting an unsynchronized manual transmission requires double-clutching to synchronize the gear speeds. Releasing the clutch pedal in neutral forces the input shaft to slow down with the engine to match the lower rotational speed required by the higher gear ratio.

Step-by-Step Solution

1
Release accelerator, depress clutch pedal, and shift gearshift lever into neutral.
Disengages power transfer from the lower gear without gear clash.
Relieves engine load on the gear teeth so the shifter moves freely into neutral.
2
Release clutch pedal while remaining in neutral.
Re-engages the clutch friction disc to the engine flywheel while the main shaft is disengaged.
Allows the transmission input shaft speed to directly match engine speed as the engine slows down.
3
Monitor tachometer and engine sound as engine RPM naturally decreases.
Engine RPM drops to the lower operating speed corresponding to the next higher gear.
In upshifting, the vehicle road speed in a higher gear demands a lower engine RPM.
4
Depress clutch pedal a second time and slide the shift lever into the higher gear.
The higher gear engages smoothly without grinding.
Momentarily decouples the synchronized rotating assemblies to allow the gear collar to slide into place.
5
Release clutch pedal and depress accelerator simultaneously.
Engine power resumes drive wheel propulsion in the higher ratio.
Completes the shifting cycle and restores forward acceleration.

Key Concept

Double-clutch upshifting procedure for unsynchronized heavy vehicle manual transmissions
Rate this question

Topics

Upshifting and Double Clutching

More questions from this topic