Ontario MTO Truck Knowledge Practice Test

When should Differential Lock never be engaged?

1. During normal driving conditions

2. When approaching a curve

3. When wheels are spinning

4. When changing lanes

The correct answer is: When wheels are spinning

Engaging the differential lock when wheels are spinning can lead to serious mechanical issues. The differential lock is designed to help enhance traction by forcing both wheels on an axle to rotate at the same speed. When a wheel is spinning, usually due to a loss of traction, engaging the lock can cause strain on the vehicle's drivetrain. It can lead to tire scrubbing, excessive wear, and could potentially cause damage to components like the differential or axles while the vehicle is in motion. In other situations, such as normal driving conditions or when approaching curves, the differential lock is typically not necessary, and using it at those times could impair handling and increase the risk of losing control. Similarly, while changing lanes, maintaining optimal maneuverability is crucial, which is compromised by a locked differential. Hence, the best practice is to avoid engaging the differential lock when wheels are spinning.