Drivetrains

Drivetrain refers to the components that transmit power from the propulsion source to the wheels. It typically includes the transmission, driveshaft, differential(s), and final drive axles. The engine or electric motor is part of the broader powertrain, but not always the drivetrain itself.

Vehicles may be front-wheel-drive (FWD), rear-wheel-drive (RWD), all-wheel-drive (AWD), or four-wheel drive (4WD). In FWD, power reaches the front wheels through a transaxle; in RWD, a driveshaft delivers torque to the rear differential; AWD uses a center differential or transfer case to share torque; 4WD often includes selectable low range and traction modes.

The transmission changes engine speed to wheel speed. Manual transmissions use a clutch and gear sets selected by the driver. Automatic transmissions rely on hydraulic and electronic controls with a torque converter or clutches. Continuously variable transmissions provide a variable gear ratio, while dual-clutch systems use two clutches for fast, seamless shifts.

Differentials split torque between wheels. An open differential allows each wheel to rotate at its own speed but can transfer torque to the wheel with less grip. Limited-slip or locking differentials improve traction by reducing slip or locking both wheels together under certain conditions, which helps maintain drive when grip is uneven.

Maintenance involves fluids and wear items: transmission fluid, differential oil, and transfer case fluid; regular inspection of clutch wear, CV joints, and driveshaft U-joints; and monitoring for unusual noises or vibrations that may indicate wear or misalignment.

Electric and hybrid drivetrains integrate motors with gearboxes or direct drive. Some EVs use single-speed reductions or multi-speed e-gearboxes, with front, rear, or dual motors. Regenerative braking and simplified mechanical layouts can improve efficiency and reduce maintenance needs in electric systems.