Final drive

In a motor vehicle, the term powertrain or powerplant describes the main components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive (drive wheels, continuous track as in military tanks or caterpillar tractors, propeller, etc.). More recently in hybrid Powertrains the battery, the electric motor and the control algorithm are also seen as elements of the Powertrain. Usually "powertrain" is used to refer to simply the engine and transmission, including the other components only if they are integral to the transmission.

A motor vehicle's driveline or drivetrain consists of the parts of the powertrain excluding the engine and transmission. It is the portion of a vehicle, after the transmission, that changes depending on whether a vehicle is front-wheel, rear-wheel, or four-wheel drive, or less-common six-wheel or eight-wheel drive.

In a wider sense, the power-train includes all of its components used to transform stored (chemical, solar, nuclear, kinetic, potential, etc.) energy into kinetic energy for propulsion purposes. This includes the utilization of multiple power sources and non–wheel-based vehicles.

The most recent developments in powertrain are driven by the electrification of it in multiple components. Electrical energy needs to be provided, usually this leads to larger batteries. Electrical engines can be found as isolated component or as part of other elements, e.g. The axle. In hybrid Powertrains the torque generated by the combustion engine and the electric motor have to be brought together and distributed to the wheels. The control of this process can be quite involved but the reward are greatly improved acceleration values as well as much better emissions.

...
Wikipedia