Rotation occurs at the same time of revolution, which automatically increases the speed of the outer wheel and speeds up the outer wheel while slows down the inner wheel, thus playing a differential role. The differential does not work in a straight line. For the vehicle as a whole, the differential is just a small assembly mounted between the two drive halves. But without it, with a rigid connection between the two drive half-shafts and the right and left wheels rotating at the same speed, the car would only travel in a straight line, without turning. The differential has played a huge role in cars since it was invented a hundred years ago by Louis Renault, the founder of the Renault Motor Company. Every car now has a differential.

As the name suggests, the purpose of a differential is to make the wheels spin differently on either side. When the car takes a turn, such as a left turn, with the centre of the curve on the left, the right wheel travels longer than the left wheel in the same amount of time, so the right wheel turns faster. To achieve this effect, you have to adjust the differential. The differential consists of the differential housing, the planetary gear, the planetary gear shaft and the half shaft gear and other mechanical parts.

After the engine power enters the differential through the transmission shaft, it drives the differential housing directly, and then transfers it to the planetary gears, which drive the left and right axle gears, thus driving the wheels. The sum of the left and right shafts is equal to twice the speed of the differential housing. When the car is moving in a straight line, all three speeds are the same. When turning, due to the change of vehicle stress, the feedback is on the left and right axle, thus destroying the original balance of the differential. At this time, the speed is redistributed, leading to the decrease of the speed of the inside wheel and the increase of the speed of the outside wheel, thus reaching the balance state again. At the same time, the car completes the turn.

Now, in addition to this basic differential, there are several other types of differential, such as central differential, limited slip differential, and so on.