What does it mean when cars are advertised with “all-wheel drive”? Is it the same as four-wheel drive? Which should you buy?
Both transmission systems deliver power to all four wheels to provide better wheel grip than conventional two-wheel drive (2WD) vehicles in slippery conditions, whether rain-soaked bitumen or a bush track. But while the benefit is the same or similar, it’s delivered in different ways that are important for the driver to understand before buying a vehicle.
It’s easiest to start with a description of four-wheel drive (4WD). This is what you get in rugged off-roader wagons like the Mitsubishi Pajero or one-tonne work utes such as the Toyota HiLux and even in luxury models like the Range Rover. This is meant for heavy-duty work, such as on farms, work sites, adventuring or towing heavy trailers.
In some vehicles 4WD will be “full-time”, meaning all four wheels are driven all the time (even when not strictly needed), while other ‘part-time’ versions will make it selectable by the driver via a lever or switch. Part-time is easier on fuel.
Whether full-time or part-time selectable, 4WD normally will be in “high range” – the normal on-road gear ratios – but what distinguishes a true 4WD is the inclusion of “low range”.
Low range is a smaller subsidiary gearbox, which multiplies the ratio of each gear to utilise engine power more effectively. The vehicle will go much slower in low range, but crawl better over slippery, rocky or steep terrain. Mostly it has to be engaged by the driver, but expensive 4WDs make it much easier with a choice of electronic pre-set modes for specific conditions as mud, sand or snow.
The driver of a 4WD usually can drive in the following modes, depending on conditions –
- 2WD high range, for normal on-road conditions
- 4WD high range, when more grip is needed in mildly slippery conditions for towing or navigating a bush track
- 4WD low range, the ultimate crawling setting for steep or slippery terrain or towing your boat on a beach. ‘Low-low’ (first gear, low range) will allow the vehicle to move barely at walking pace, but overcome the most difficult obstacles.
All-wheel drive (AWD) is intended more to provide the security of extra wheel grip to ordinary cars or light-duty Sport Utility Vehicles (SUVs, or ‘soft-roaders’) in mostly normal conditions.
Some cars, such as Audi’s quattro and all Subaru sedans and wagons, have full-time, or permanent, AWD. This is considered to be a valuable safety benefit, as it ensures optimum tyre grip even in a passing shower. The driver may or may not be aware of this extra grip, but the safety is there.
More often, AWD comes as a part-time or ‘on-demand’ feature in SUVs. Normally, the vehicle travels in default 2WD front-drive mode, but when conditions turn slippery electronic sensors detect the loss of grip and engage the rear wheels in milliseconds.
On-demand AWD is automatic and seamless, requiring no action by the driver. However, some SUVs offer additional controls for drivers to manually select and hold AWD.
This means there are some SUVs capable of being used for more than school-run taxis. They won’t pull a 2-tonne boat to Fraser Island, but – thanks to incredibly sophisticated and sensitive electronics – will provide most drivers all the capability they need for light-duty weekend adventuring.
AWD or 4WD? Buy 4WD if you intend to do serious off-road driving or heavy towing. If you don’t, buy AWD and save on fuel and other ‘heavy-duty’ costs like tyres. AWD is all you need if you’re a weekend adventurer or just want extra day-to-day security, but remember, AWD systems on some SUVs have more features than others.
What do you prefer? AWD or 4WD? Let us know!