Though similar in principle, the intent of All-Wheel Drive (AWD) and Four-Wheel Drive (4WD) vehicles are very different. One is used for enhancing traction in all situations, while the other is intended specifically for off-road performance.
The first four-wheel systems were used on electric cars in the late 1800s, and AWD was first used by Audi in the late 1970s for rally racing.
4WD PurposeAWD is a type of 4WD system, and like traditional 4WD, is used to distribute power among all four of a vehicle's wheels for traction.
Traditional 4WD systems use a transfer case that completely locks the front and rear axles together for better off-road traction. AWD uses a center differential similar to those found in the axles to allow the axles to turn at different rates.
Because the axles are locked together, 4WD systems are better for hard-core off roading, rock-climbing and fording mud and water.
AWD systems are more geared for on-road handling, and can allow infinite variation of power split between front and rear axles. This allows an AWD car to have the stability of a front-drive car, with the cornering ability of a rear-drive one.
