What is the primary function of the differential in a drive axle?

• A. Increase engine torque
• B. Allow wheels to rotate at different speeds
• C. Reduce fuel consumption
• D. Prevent gear wear

Answer: (B)

A differential lets the two wheels on an axle rotate at different speeds. When you turn, the outside wheel has to travel a longer distance than the inside wheel, so it must spin faster. If both wheels were forced to spin at the same rate, they'd scrub against the road, causing tire wear and extra stress on the drivetrain. The differential uses gears to split power and allow each wheel to turn at its own appropriate speed while still delivering torque from the engine. This makes turning smooth and reduces unnecessary wear. The other options describe effects or actions handled by other parts of the system (engine torque, fuel efficiency, or protection against wear) rather than the differential’s primary job.