Examkin

Question

Difficulty: EasyUpshifting and Double Clutching

Most heavy commercial motor vehicles are equipped with unsynchronized manual transmissions. Why is the double-clutching technique required when shifting gears in these vehicles?

  1. A
    To engage the clutch brake during each gear transition to prevent transmission wear
  2. To match the engine speed with the transmission gear speed so the gears mesh smoothlyAnswer
  3. C
    To keep the engine operating continuously at its maximum governed RPM
  4. D
    To disconnect the drive axle differential gears so the driveshaft can freewheel

Answer

To match the engine speed with the transmission gear speed so the gears mesh smoothly
Because heavy commercial vehicles typically use unsynchronized manual transmissions, the driver must double-clutch to align the speed of the engine and transmission input shaft with the gear speed, allowing gears to engage smoothly without grinding.

Step-by-Step Solution

1
Identify the mechanical design characteristic of commercial manual transmissions.
Heavy-duty commercial vehicles use unsynchronized transmissions that lack synchronizer cones or rings.
Without synchronizers, transmission gears cannot automatically align their rotational speeds during shifting.
2
Determine the functional purpose of double clutching.
Releasing the clutch in neutral connects the engine to the transmission input shaft, allowing the driver to match the rotational speeds before engaging the next gear.
Speed synchronization allows gear teeth to mesh smoothly without grinding or causing mechanical damage.

Key Concept

Purpose of Double Clutching in Unsynchronized Manual Transmissions
Estimated Time:45s
Rate this question

Topics

Upshifting and Double Clutching

More questions from this topic