What is a Differential?

The differential is a device that splits the engine torque two ways, allowing each output to spin at a different speed.

The differential is found on all modern cars and trucks, and also in many all-wheel-drive (full-time four-wheel-drive) vehicles. These all-wheel-drive vehicles need a differential between each set of drive wheels, and they need one between the front and the back wheels as well, because the front wheels travel a different distance through a turn than the rear wheels.

差速器（英语：Differential）的发明，是因为在汽车于转弯时，外侧轮子走的路径要比内侧轮子走的路径要大，所以如果汽车想顺畅和精确的转弯，便需要一个装置能够转换和允许内外侧车轮以不同的速率进行旋转，从而以不同的转速来弥补距离的差异。