How to use your 4WD system

WITH CROSSOVERS AND SUVS supplanting sedans as the default choice for everyday transportation, it’s common for any given vehicle to sport fouror all-wheel drive (4WD and AWD). Most new models have fully automatic AWD systems that will detect wheel slip and automatically divert power to the wheels with traction, with no driver involvement required. But in most bakkies and some SUVs with 4WD, there will be at least two drive configurations you can choose from to maximise your vehicle’s capability in a given situation. If you drive an SUV with an off-road bent, such as a Toyota Land Cruiser, you have even more choices – high range, low range, locked or unlocked centre differential. It gets complicated quickly.

But let’s begin with the biggest topic of confusion: 4WD versus AWD. With AWD, there’s a centre differential that allows the front and rear tyres to rotate at different speeds. For commuting to work in 8 cm of sleet, for example, AWD will keep you safe. Driving on something trickier than a slightly muddy or snowy path? You’ll want 4WD, to eliminate slip in the system front-to-rear. If you’re ready to find out what your 4WD system can do, start here.

If you have a 4WD vehicle with knobs or buttons that let you choose between twoand four-wheel drive, and you’re on a normal road, use 4WD Auto. Both 2WD and 4WD Auto are fine for dry tarred surfaces. The only advantage of running in 2WD would be some marginal fuel-economy benefit, or saving wear on the front-drive system. But if it starts raining, already being in 4WD Auto means that extra traction will be there to save you, before you remember that you might need it.

4WD High locks the front and rear axles together, which is useful in only a few situations. For example, somewhere lowtraction, but high-speed – probably off-road, like a desert wash. Here, 4WD High tends to feel more stable, since the vehicle won’t want to turn. But most of the time, if you have both, you’re better off in 4WD Auto, letting the system send power forwards or back as needed. A friend used to have a late-’70s Jeep Cherokee with 4WD Auto. The only time he needed to switch it into 4WD High was when he (successfully) drove through a large body of relatively deep water.

4WD Low uses gearing to multiply torque to the wheels, useful for slow trails or towing a boat out of the water. But generally, Low is strictly for slow off-roading, which is why it’s usually relegated to bakkies and SUVs that have serious off-road pretensions. A Toyota Hilux would have it, but a RAV4 wouldn’t. One use case for this setting: soft-sand driving, where you want all the torque and traction you can get. Once in 4WD Low, you should also lock the rear differential, usually a switch on the dash with four tyres and a little ‘×’ between the rear ones. This locks the rear wheels side-to-side, which can be handy because if one side loses traction, the opposite side keeps turning, powering you forwards. (Just don’t use the diff lock on a corner, because the whole point of a differential is to allow your car to make a smooth turn, with the outside tyre turning faster than the inside.) There are also a few vehicles with a front differential lock, but if you bought one of those, then you probably know how to use it already.