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Question

Difficulty: MediumUpshifting and Double Clutching

While accelerating a commercial motor vehicle equipped with an unsynchronized manual transmission, you observe the tachometer reach the manufacturer's recommended shift point. After taking your foot off the accelerator, pressing the clutch pedal, and moving the gear shift lever into neutral, what action must you take next before shifting into the higher gear?

  1. A
    Keep the clutch pedal held firmly to the floor while accelerating the engine to match road speed.
  2. Release the clutch pedal fully and allow both the engine and transmission input shaft speeds to decrease.Answer
  3. C
    Press the accelerator pedal sharply while remaining in neutral to synchronize internal gears.
  4. D
    Depress the clutch pedal all the way to the floorboards to engage the clutch brake before making the shift.

Answer

Release the clutch pedal fully and allow both the engine and transmission input shaft speeds to decrease.
Releasing the clutch pedal fully while the transmission is in neutral connects the transmission input shaft back to the engine. As engine RPM drops with the throttle released, the input shaft speed decreases simultaneously until it matches the required rotation speed of the higher gear.

Step-by-Step Solution

1
Identify the initial phase of the double-clutch upshift sequence.
The driver has released the throttle, pressed the clutch, and shifted the transmission into neutral.
This disengages the lower gear and moves the gear shift assembly into a free state.
2
Determine the necessary intermediate mechanical synchronization step.
The driver must release the clutch pedal fully while remaining in neutral without pressing the accelerator.
Because higher gears require a lower engine and input shaft RPM for a given road speed, letting the clutch out in neutral allows the engine and input shaft to slow down together to the matching speed.
3
Complete the upshift progression.
Once RPM has dropped to the target level, depress the clutch pedal again, push the lever into the higher gear, and smoothly release the clutch while reapplying throttle.
This locks the transmission into the higher gear cleanly without grinding gears.

Key Concept

Double-Clutch Upshifting Sequence and Mechanical RPM Synchronization
Estimated Time:1m 0s
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Topics

Upshifting and Double Clutching

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