Four-wheel drive, All-wheel drive, AWD, 4WD, or 4x4 ("four by four") is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously. While many people associate the term with off-road vehicles and Sport utility vehicles, powering all four wheels provides better control than normal road cars on many surfaces, and is an important part in the sport of rallying.
4WD versus AWD
All wheel drive or AWD means that the vehicle is designed to provide power to all four wheels at the same time, and in most cases cannot be switched to the two wheel drive (2WD) option. The distribution of power to the front set and hind set of wheels differs from one system to another. 4WD or four wheel drive (part time and full time) also means the vehicle has a drivetrain that allows all four wheels to receive torque from the engine simultaneously. AWD and full time 4WD essentially mean the same thing except for some difference in the power settings. 4WD has three settings: 2WD (two wheel drive), low and high whereas in case of AWD, the 2WD option is absent
Four-wheel Drive (4WD)
Most 4WD layouts are front-engined and are derivatives of earlier front-engined, two-wheel-drive designs. They fall into two major categories: * Front-engine, rear-wheel drive derived 4WD systems, standard in most sport utility vehicles and in passenger cars, (usually referred to “front engine, rear-wheel drive/four-wheel drive”), forerunners of today's models include the Jensen FF, AMC Eagle and Mercedes-Benz W124 with the 4Matic system and Suzuki Grand Vitara with/without 4 mode transfer case. * Transverse and longitudinal engined 4WD systems derived almost exclusively from front-engined, front-drive layouts, fitted to luxury, sporting and heavy duty segments, for example the transverse-engined Mitsubishi 3000GT VR-4 and Toyota RAV4 and the longitudinal-engined Audi Quattro and most of the Subaru