Drivetrain

The drivetrain of a motor vehicle is the group of parts that deliver power to the wheels that move the vehicle.^[1] The drivetrain includes the transmission or transaxle, driveshafts, differentials, axles and wheels.^[2] It does not include the engine or motor that creates the power.^[2] In contrast, the powertrain includes the engine and the drivetrain. In order to transmit power from the engine to the rear wheels, the drivetrain uses some of that power to work.^[3] Drivetrain loss is the power lost, measured in horsepower, between what the engine generates and what is available at the wheels.^[4] As power is transmitted through the drivetrain, forces including inertia, drag and friction cause some power to be wasted.^[4] The more component parts power is transmitted through, the more power is lost. However each combination of drivetrain parts is different as to how much is lost.^[4] The automatic transmission wastes the most power of any drivetrain component.^[3]