fourbyfour

Four-by-four, or fourbyfour, is a term for a vehicle drivetrain configuration in which power can be delivered to all four wheels. The term is used interchangeably with 4x4, four-wheel drive (4WD), and is associated with off-road capable vehicles such as SUVs and pickups. In standard practice, a four-by-four system uses a transfer case to split power between the front and rear axles, and often allows selection between high-range and low-range gears. Distinguish it from all-wheel drive (AWD), which provides continuous power distribution to all wheels for on-road use and often lacks a low-range gear or a lockable center differential.

Equipment may include manual or electronic engagement, front and rear differentials, and locking differentials to maximize traction. Part-time 4WD systems require user input to engage; full-time or on-demand systems engage automatically as conditions change.

Historically, 4x4 technology originated for military and agricultural use, with early models appearing in the mid-20th century. The Jeep, Land Rover, and later brands such as Toyota, Ford, and Chevrolet popularized civilian four-by-four vehicles, especially in regions with rough terrain or poor road access. Today, four-by-fours are common in consumer markets, prized for off-road capability, towing, and safety in adverse weather. They vary widely in complexity, from mechanical transfer cases to electronic torque-vectoring systems. The term remains widely used in British English, while 4x4 is common in American and international usage.