Six-wheel drive (6WD or 6×6) is an all-wheel drive drivetrain configuration of three axles with at least two wheels on each axle capable of being driven simultaneously by the vehicle's engine.
When it has ten – with two pairs of ganged "dual" wheels on each rear axle as on a GMC CCKW – all are also driven but the 6×6 designation remains.
Heavy hauler and ballast tractor 6×6s have had a long history as prime movers both in the military (as tank transports and artillery tractors), and commercially in logging and heavy equipment hauling both on- and off-road.
Most six-wheel drive vehicles have a forward axle and two at the rear (with only the front pair steering), or three evenly spaced in varying steering configurations.
Military Military/commercial Commercial Conversions Recreational ATV/UTV Concept car, testbed, and limited production commercial examples include: Twin front axle Twin rear axle (Twin axle) drive in the rear, and an integrated "roll steer" function built into the suspension design.