Which dashboard gauge can help you decide when to upshift?
- The clock
- The speedometer
- The coolant temperature gauge
- The tachometer ✓
Answer: D. The tachometer
The tachometer is the gauge that helps you decide when to upshift, because it shows engine speed in r.p.m.
Why this is the answer
The handbook's shifting section says to use a tachometer, which indicates engine speed, to decide when to shift, and it gives examples of upshifting at specific r.p.m. figures. It also explains that r.p.m. means revolutions per minute, the number of turns the crankshaft makes in a minute, and that most trucks have a tachometer in the instrument panel for this. Since shift points are given in engine r.p.m., the gauge that reads that value is the one you watch.
Why the other answers are wrong
- A. The clock — A clock only tells you the time of day and has nothing to do with engine speed or shift points.
- B. The speedometer — The speedometer shows how fast the vehicle is moving, while the passages tie shifting decisions to engine r.p.m. rather than road speed.
- C. The coolant temperature gauge — The coolant temperature gauge reports engine temperature, not engine speed, and the passages never connect it to choosing a shift point.
Remember it
Shift by the dial that counts engine turns, not the one that counts miles per hour.