Commercial Driver License (CDL) Class B Practice Test

When should you downshift automatic transmissions?

1. When going up hills

2. When going down grades

3. When starting from a stop

4. When reaching high speeds

The correct answer is: When going down grades

Downshifting in automatic transmissions is primarily necessary when going down grades. This action helps to maintain control of the vehicle's speed without relying solely on the brakes, which can overheat and fade during prolonged use. By downshifting, the engine can assist in decelerating the vehicle through engine braking, allowing for a safer descent, especially on steep inclines. In the context of driving, utilizing engine braking as a method to manage speed on downhill slopes is vital for safety. It reduces wear on the braking system and enhances control, particularly in large vehicles, which can gain momentum quickly when descending. Other scenarios such as going up hills, starting from a stop, or reaching high speeds typically do not require downshifting in the same way. Upshifting might be more relevant when climbing because it allows the vehicle to gain speed efficiently. Starting from a stop involves more about engaging the transmission correctly rather than downshifting, and reaching high speeds usually means staying in a higher gear for optimal performance and fuel efficiency.