The terms four-wheel-drive (4WD) and all-wheel-drive (AWD) sound alike and both seem to do the same thing. But look a little harder, and you will find differences.

At a glance, AWD vehicles can have permanently engaged or automatically engaging four-wheel-drive capability. They are designed to operate with all wheels propelling the vehicle under all driving conditions.

The term 4WD was originally used to describe early Jeeps and trucks which had systems to apply power to all four wheels by moving an interior shift lever to manually “lock” the vehicle’s hubs. Today, 4WD generally refers to vehicles that can operate in two- or four-wheel-drive.

Part-time 4WD
This is the most basic system where the driver can change the vehicle from a two-wheel to four-wheel mode by moving a shift lever or pressing a button inside the vehicle. By locking the front and rear axles together, the front and rear wheels rotate at the same speed to improve straight-line traction.

Part-time systems shouldn’t be engaged unless the vehicle is on very slippery road conditions such as deep snow and mud as this system has no centre differential.

Permanent 4WD
Vehicles with permanent 4WD (also known as full-time 4WD) is a system that powers all four wheels at all times. They always operate with power going to all four wheels, so drivers benefit all the time from four-wheel traction and don’t have to shift or push a button to activate it.

In contrast with part-time four-wheel drive, vehicles with permanent four-wheel drive have a centre differential, so they can travel on dry pavement without damaging components or having wheels bind during turning or cornering.

Automatic 4WD
This system automatically monitors traction needs, and decides when and where to apply torque to different wheels for drivers. In some models, the driver can set the car to “automatic 4WD” mode, and the vehicle will decide for the driver. In other vehicles, the system is entirely automatic.

AWD
All-wheel drive works like a permanent 4WD system by providing continuous power to front and rear axles. This system is designed to function on all types of surfaces, both on- and off-road, and usually cannot be switched off.