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Difficulty: EasyUpshifting and Double Clutching

While accelerating a commercial motor vehicle equipped with a manual transmission, which two primary indicators should a driver monitor to know when to upshift?

  1. A
    Engine oil pressure and engine coolant temperature
  2. Engine speed (RPM on the tachometer) and road speed (MPH on the speedometer)Answer
  3. C
    Primary air reservoir pressure and brake application pressure
  4. D
    Exhaust gas temperature and odometer trip mileage

Answer

Engine speed (RPM on the tachometer) and road speed (MPH on the speedometer)
According to the CDL manual, there are two primary ways to know when to upshift: monitoring engine speed (RPM) on the tachometer to shift when the engine reaches the top of its operating range, and monitoring road speed (MPH) on the speedometer to shift at the speed range appropriate for the next gear.

Step-by-Step Solution

1
Identify the primary methods described in standard commercial driving manuals for knowing when to upshift.
The two standardized methods are monitoring engine RPM using the tachometer and monitoring vehicle speed using the speedometer.
Commercial diesel engines operate efficiently within a narrow RPM band, and each gear corresponds to a specific road speed range.
2
Evaluate the gauges that provide real-time mechanical feedback for gear synchronization.
The tachometer indicates when engine speed reaches the top of the manufacturer's recommended operating range, while the speedometer indicates when road speed matches the entry speed for the next higher gear.
Other cab instruments (such as temperature, oil pressure, or air pressure gauges) monitor vital safety and support systems but do not determine shift timing.

Key Concept

Methods for determining upshift points
Estimated Time:45s
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Topics

Upshifting and Double Clutching

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