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What is a limited-slip differential?

“A limited-slip differential is a device that calculates and redistributes power by shifting a different amount of torque among the wheels to avert the loss of traction.”

In normal driving, the rotational speed of the left and right wheels remains the same, but when driving on snowy, icy, sandy, or muddy roads, a difference in the number of rotations between the wheels on each side arises. The same also occurs when turning corners. The outer wheel rotates more because its turning distance is longer than that of the inner wheel. Therefore, differentials are needed to transfer a different amount of power to the wheels. Limited-slip differentials serve to prevent traction loss and obtain the optimal distribution of power by adjusting the torque among wheels. They allow the wheel with traction to get more torque so that the car keeps on moving.

Limited-slip differentials combine characteristics of an open differential that allows each wheel to spin independently, and a locked differential that makes the rotational speed of each wheel the same. If more grip for a certain wheel is considered necessary, the device adds pressure to the wheel with less grip, and the wheels become locked together, making them unable to spin at overly different rates. This enables the wheel with more traction to put torque down. When turning a corner, the grip of the inner wheel weakens, and the wheel can slip. In this case, the device shifts the torque to the inner wheels to prevent slippage and redistributes the torque to the outer wheels.

There are two types of limited-slip differentials: electronic and mechanical limited-slip differentials. The former, also called e-LSD, uses an electronically controlled clutch to actively manage the rotational speed of wheels. In other words, the car identifies the road conditions and operates the e-LSD in advance. The latter, named M-LSD, employs a mechanically controlled clutch to control the traction of the wheels. The device distributes the power, but only operates when it notes a difference in the wheels’ rotational speed on each side after it reaches a certain level. That is, M-LSD only works when a wheel slips. Another limitation is that the degree to which the power is limited is mechanically determined. Therefore, e-LSD is considered smarter than M-LSD, and it operates more smoothly and accurately.
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