Chapter 2-4: Inter-axle differential lock

The “Inter-axle Differential Lock” section of the Ontario truck driver knowledge test evaluates a driver’s understanding of this important traction control feature in commercial vehicles.

Ontario Truck Driver Test - Chapter 2-4: Inter-axle differential lock

1 / 5

Under normal driving conditions, in which position should the inter-axle differential lock control valve be kept?

It doesn’t matter

Lock

Halfway between lock and unlock

Unlock

2 / 5

Why should unnecessary use of the differential lock be avoided?

It can result in tire wear and axle strain

It causes the steering wheel to lock

It will immediately damage the engine

It disables the vehicle’s braking system

3 / 5

What is the primary purpose of the inter-axle differential lock on vehicles with tandem rear axles?

To control the vehicle’s braking system

To improve fuel efficiency on highways

To lock the differential so power is transmitted equally to both axles

To reduce engine noise at high speeds

4 / 5

Which of the following is a caution related to using the inter-axle differential lock?

Do not activate the differential lock when the wheels are actually spinning

Never operate the valve to see if it moves freely

Use the lock to increase tire wear for better traction

Always leave the differential locked at highway speeds

5 / 5

When should you use the lock position of the inter-axle differential lock?

Only when approaching conditions where one or both wheels of an axle may slip

Only when parked

At all times when driving on dry pavement

Only when driving downhill

Your score is

The inter-axle differential lock helps distribute power evenly to both axles, which is essential for maintaining traction on slippery or uneven surfaces. Drivers must know when and how to engage and disengage the lock safely, as improper use can damage the drivetrain. The test covers recognizing ideal situations for using the lock—such as on snow, mud, or loose gravel—and stresses the importance of disengaging it on dry, paved roads. Mastery of this section enhances vehicle safety and control.