Nowadays, this has changed dramatically, and vehicles of all sizes are available with either all-wheel drive (AWD) or four-wheel drive (4WD), becoming far more desirable than those driven by the front or rear wheels.
What is AWD, and how does it work?Generally, these drivetrains power both the front and rear wheels with no input from the driver, although some vehicles have selectable modes which can be used to modify power delivery electronically.
These systems are split into two categories, part-time AWD and full-time AWD. The first sends torque to two driven wheels in normal driving conditions and automatically engages the other two when additional traction is needed, using a suite of sensors and electronic controls. Full-time AWD drivetrains are more straightforward, sending power two all four wheels continuously.
What is 4WD, and how does it work?This system predates AWD, and it was traditionally used on big, off-road capable vehicles. Obviously, it sends torque to all four wheels as well, using a series of front, rear, and central differentials, transfer cases, and couplings to maximize traction.
These drivetrains tend to be sturdier, rely on fewer electronics, and generally more suited for off-road use than their AWD counterparts. For this reason, many also have low and high gear ranges that can be selected either via a switch or a mechanical lever.
Drivers can engage and disengage 4WD through a button, switch or shift lever and some systems also allow them to lock the differentials for extra torque in extreme off-road conditions.
As the name implies, full-time 4WD sends torque to all four wheels on a permanent basis. Most modern systems offer a choice of driving modes that modifies the amount of power sent to each axle.
So, which one is better for me?The answer to this question depends on the vehicle and where you generally drive it. If you mostly spend time driving on paved roads and light trails and you want a compact vehicle, then AWD is better for you.
On the other hand, if you live in a remote area and/or enjoy off-roading, you’re better off with a 4WD truck or SUV. This system is also generally better suited for deeper snow and more extreme winter conditions, so if you live in an area where winters are long, a 4WD vehicle is exactly what you need.