How Does 4-Wheel Drive Work? Here’s Your Guide

Back in the day, 4-wheel drive and all-wheel drive were niche features. Unless you had a truck or an oddball vehicle like an Eagle wagon or Audi 4000, your vehicle was two-wheel drive. Now, with crossovers and SUVs supplanting sedans as the default choice for everyday transportation, it’s common for any given vehicle to sport a quartet of driven wheels. But that doesn’t mean all systems are created equal.

Unless you have a fully automatic all-wheel-drive system, there will be at least two drive configurations you can choose to maximize your vehicle’s capability in a given situation. If you drive an SUV with an off-road bent, like a Toyota Land Cruiser, then you’ll have more complicated choices—high range, low range, locked or unlocked center differential.

Then, there are all-wheel-drive vehicles with a two-wheel-drive mode (like the Chevy Equinox) and trucks and SUVs that offer all of the above.

Let’s begin with the main topic of confusion: 4-wheel drive versus all-wheel drive. Is 4-Wheel Drive or All-Wheel Drive Better?

Whether you want 4-wheel drive or all-wheel drive depends on the situation. Commuting to work in three inches of sleet? In that case, AWD is the hot setup. Off-roading, then 4-wheel drive is the choice.

Back in the early days of the SUV, four-wheel traction meant 4-wheel drive. Most systems these days are AWD, meaning that there’s a center differential of some sort that allows the front and rear tires to turn at different speeds. AWD can be used on dry pavement, where 4-wheel drive requires a slippery surface so that the front and rear ends can match speed without binding.

Most modern crossovers are AWD, and don’t offer the option to disengage the system—they just work automatically, as needed, when they detect slip. But even if you have that sort of system, there’s something you need to know. If you’ve got a vehicle that offers two-wheel drive or 4-wheel-drive auto, then most of the time you may as well use the 4WD Auto setting. It’s fine for dry pavement, so the only advantage of running in 2WD would be some fractional fuel economy benefit—or saving wear on the front-drive system. Meanwhile, 4WD Auto is handy even if it starts raining—your extra traction will be there, on demand, automatically.

4WD High is a setting rarely needed, if you’ve got a system that offers 4WD Auto. That’s because it just locks the front and rear end together, which might be useful in some narrow off-road context but isn’t doing anything for you on that snowy road. In fact, I’d rather have the system sending power forward or back as needed most of the time, even off-road.

What About This 4WD Low Range? Without an Auto setting, 4WD High is what you’d use in any situation that’s low-traction but relatively high-speed—a dirt road or snowy paved road. 4WD Low is strictly for slow off-roading or places where torque multiplication would really help you out (like deep sand). Low range used to be common, but these days it’s relegated to pickup trucks and SUVs that have serious off-road pretensions. A Toyota 4Runner would have it, but a Highlander won’t.

OK, let’s say you’re venturing off-road—a little beach driving. This isn’t an off-road instructional but we’ll assume you let some air out of your tires. Good. Now, what does that rocker switch on the dash do? The one that shows four tires with a little “X” between the rear ones? That’s your rear differential lock, and it can be handy.

Just as 4WD High locks the front and rear axles together, the rear diff lock connects the rear end side-to-side. That means that if one side loses traction, the opposite side keeps spinning, powering you forward. It’s a great feature, provided you’re driving straight.

You don’t really want to use your 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 tire turning faster than the inside. Lock them together and your car won’t want to turn. And when it does, it’ll judder and skid in protest.

There are also a few vehicles with a front differential lock, but I’m going to assume that if you bought one of those then you probably know how to use it.

Important note: before you go off-road, set your traction control, which likely means disabling it. The button usually has some squiggly lines on it. That’s your stability-control-defeat button. Stability control will try to keep your tires from spinning. If you’re on a rocky trail, that can be great—by grabbing the brakes at individual corners, stability control can sometimes mimic the benefits of locking differentials. But if you’re in mud, sand, or snow, stability control might get you stuck, even if you’ve got 4-wheel drive. That’s because in certain circumstances, you want wheelspin and momentum. Out on the sand, your stability control system will detect wheelspin and cut power to the spinning wheels. Which, in that context, will be all of them. Then you grind to a halt. To turn off the system, you usually hold down the button for at least five seconds. First the, traction-control system will deactivate (sometimes just with a push of a button) but you want the whole thing off, so hold down the button until you see a message like “stability-control system disabled.” Some cars, like Volvos, might not have a dedicated button, but stability control disable is always there somewhere, even if it’s buried five screens deep in a touchscreen menu.

One more thing: the price of your 4x4 often has a direct correlation to the complexity of its drive systems. And we can’t really explain all of them on a case-by-case basis, but if you purchase a machine with overt off-road pretensions, it behooves you to study up on its capabilities.

A  Mercedes GLE 450 with the optional hydropneumatic suspension can bounce itself out if it gets stuck. The Ford Raptor offers something called Baja mode, which activates an antilag system for the turbos—yee haw. And the Land Cruiser has a button for off-road turn assist, which brakes the inside wheels to give you a skid-steer effect and tighten your turning circle on loose surfaces. But to activate it, you'll need to be in 4WD Low and using Crawl Control, which is like an off-road cruise control system.

Point is: whatever your rig, step one should probably be opening your glove box and reading the owner’s manual.