The power train serves two functions:it transmits power from the engine to the drive wheels,and it varies the amount of torgue.传动系有2个功能：它传递来自发动机的动能到车轮，还有它能变化扭矩的输出。

The power train includes传动系包含：（1）engine发动机：that produces power 它产生动能。（2）transmission变速箱：either manual or automatic 不是手动变速箱就是自动变速箱。（3）clutch 离合,used only on manual transmission仅用于手动变速器,or torque converte或者液力变矩器,used only on automatic transmission仅用于自动变速器。(4)drive shaft传动轴：that transmits the power from transmission to differential它传递来自变速箱的动能到差速器。（5）differential差速器：它传递动能到2条半轴（驱动动)。