AWD (vehicle)
An AWD vehicle (short for All-wheel drive vehicle) is one with a powertrain capable of providing power to all its wheels, whether full-time or on-demand.
The most common forms of AWD are:
4×4, also known as four-wheel drive and "4WD", reflecting two axles with both wheels on each capable of being powered.
6×6, also known as six-wheel drive and "6WD", reflecting three axles with both wheels on each capable of being powered
8×8, also known as eight-wheel drive and "8WD", reflecting four axles with both wheels on each capable of being powered
Vehicles may be either part-time all-wheel drive or full-time:
On-demand, also known as "part-time", where one axle is permanently connected to the drive, the other is being connected as needed
Full-time, also known as "permanent", where axles are permanently connected, with or without a differential.
Usage of the terminology
Today, the designation AWD is becoming narrowed, particularly in the US, to apply to vehicles with drive train systems that have permanent drive and usually include a differential between the front and rear drive shafts. However, the designations AWD and "all-wheel drive" long predated the trend, Associated Equipment Company (AED) building AWD trucks in conjunction with FWD (UK) in 1929, and General Motors manufacturing a line as "all-wheel drive" as early as the late 1930s. This distinction in terminology is not generally used outside the USA.
