Differential Steering Explained by Chevrolet’s Film 1973

Ever wonder how the wheels on your car work and how they’re not slipping when you’re cornering? Back in 1937, the Jam Handy Organization worked with General Motors to release a short video explaining how the rear-axle differential works.

When a vehicle turns into a corner, the rear wheels travel basically at different speeds. The outer rear wheel has to spin faster and traverse a farther distance to keep up with the inner wheel’s movement. This problem was solved back then by connecting only one rear wheel to the engine, allowing each rear wheel to turn separately.

However, connecting only one wheel to the engine proved to be too much of a burden. The connected wheel has to do all the work to get the vehicle moving and grip problems started to arise. Soon, manufacturers dispatched this solution and looked for a better one.

Connecting both rear wheels to a single axle so that they will turn at the same time, resulted in one wheel sliding while the other makes the turn. Engineers had to find ways to connect both wheels to the engine to generate enough torque while preventing the wheels from sliding on turns.

This dilemma produced what we call the ‘differential’ part of the rear axle and it’s still being used today.

The differential allows the rear wheels to move at varying speeds. Each wheel on your car rotates on separate axles which are all mounted on a steady frame, allowing each wheel to spin independently and at differing speeds. Spokes are attached at the end of each axle to allow the engine to control each wheel. A separate pivoted spoke is situated between the two to allow one power source to drive both wheels as the vehicle moves.

After the essential concepts of the rear differential have been established, manufacturers started using metallic gears to make the differential system more durable and precise. More and more spokes are added to make its movement smoother and quieter.

Archaeological evidence and historical claims state the possibility of differentials being used way before it was invented for vehicles. The oldest discovery so far is the Antikythera mechanism which is dated to have existed around 100BC. The device is presumed to have been used to determine the moon’s phase and the Sun and the Moon’s position during an eclipse.

To date, the only confirmed use of a differential system long before it was used in automobiles, was back in 1720, when one Joseph Williamson used it in a clock that mimics a sundial’s readings.

Watch the video clip of ‘Around the Corner’ below to understand more about differentials.