因为汽车比较重，刹车系统也不如今天的有效，以前的汽车必须利用变速箱(或更准确地说，引擎压缩)帮助汽车减速。

Because cars used to be heavy and braking systems were not as efficient as they now are, it was necessary to use the gears (or to be more precise, the engine compression) to help to slow the car down.

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变速箱零件的配合面、压缩机零件的平面、轴端面等。

Transmission component mating plane, compressor component plane, and shaft ends.

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