Understanding 4x4, Four-Wheel, All-Wheel, Etc.
Although the terms 4x4 (four-by-four), four-wheel drive (4WD), all-wheel drive (AWD) and individual-wheel drive (IWD) are often used interchangeably and refer to the class of vehicles with the ability to drive on all four wheels, they have different meanings. To understand the difference, which is crucial in the selection of such a vehicle, we will therefore take a look at the definitions of the mentioned terms.
4x4
The term encompasses all vehicles with total 4 wheels powered - supercars, SUVs, crossovers, family cars, city cars … The main purpose of the term 4x4 is to distinguish these vehicles from two-wheel drive automobiles with front- or rear-wheel drive system or 2x4. The term 4x4, however, reveals nothing about the technology of the system.
4WD
Four-wheel drive or 4WD is used to describe vehicles with the ability to drive on all four wheels through transfer case which means that the front and rear shafts are locked if engaged. However, it is most often used to distinguish between cars with selectable four-drive and permanent four-wheel drive or all-wheel drive (AWD).
AWD
As mentioned above, AWD refers to vehicles with permanent four-wheel drive. Unlike 4WD, AWD cannot be disabled because it doesn’t work through transfer case but instead, it is based on a differential between the drive shafts. Typically, AWD vehicles also include anti-slip technology to increase safety in the event one of the wheels loses traction.
IWD
IWD (abbreviation for individual-wheel drive) has been introduced relatively recently to describe vehicles featuring an electronic motor on each of the wheels. The system is very similar to 4WD but because it uses electric motors, it can have a negative torque. Please note that the term IWD isn’t used for 4x4 vehicles exclusively.
Differences in Understanding between Different Countries
Although the terms discussed above are used to differentiate between vehicles with the ability to drive on all four wheels based on the technology used, they tend to be understood differently in different countries. For example, in Australia, AWD can be understood as a vehicle that isn’t the most appropriate for off-road driving. In North America, AWD is sometimes used as a synonym for SUV. Another example is 4x4 which is sometimes understood as four-wheel drive. You may also come across the term 4-wheeler which most often refers to all-terrain vehicles, including those with two-wheel drive.