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How to Use Your 4WD System

Popular Mechanics logo Popular Mechanics 4 days ago Ezra Dyer
a close up of a camera: How to Use Your 4WD System© Nissan How to Use Your 4WD System

Back in college, I was riding with a friend on our way to go skiing when we abruptly spun off a snowy Maine road and skidded backwards through the (thankfully) empty parking lot of a paper mill. Somewhere in the middle of the second full pirouette I wondered how this happened, given that the vehicle in question was a four-wheel-drive Grand Cherokee. Once we came to a stop, unscathed, I asked that question out loud. "Oh yeah," said my friend, pulling back on the stubby lever next to the shifter. "I guess it helps if you're actually in four-wheel-drive." That was the first in many subsequent lessons that fall under the title: "Four wheel drive is great-if you know how to use it."

a truck driving down a dirt road: Put your vehicle in four-wheel drive before you get stuck.© PeopleImages - Getty Images Put your vehicle in four-wheel drive before you get stuck.

Since the days of that first-generation Grand Cherokee, four-wheel-drive systems have evolved. The biggest difference is that most systems these days are all-wheel-drive, meaning that there's a center differential of some sort that allows the front and rear tires to turn at different speeds. All-wheel-drive can be used on dry pavement, where four-wheel-drive requires a slippery surface so that the front and rear ends can match speed without binding. Most modern crossovers are all-wheel-drive 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. More on that in a moment.

Trucks and larger SUVs, tend to offer three or four settings for their four-wheel-drive systems: 2WD, 4WD Auto, 4WD High and sometimes 4WD Low.

2WD, 4WD Auto or 4WD High?

a close up of a car: How to Use Your 4WD System© GMC How to Use Your 4WD System

Let's start with the first two. If you've got a vehicle that offers two-wheel-drive or four-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 (since these vehicle tend to be truck-based and thus rear-drive when they're in two-wheel-drive mode). Meanwhile, 4WD Auto is handy even if it starts raining-your extra traction will be there, on demand, automatically.

Four-wheel-drive high is a mostly useless setting 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. I had a friend who used to have a late-70s Jeep Cherokee that was all-wheel-drive (so, 4WD Auto) and the only time he needed to lock the four-wheel-drive system was when he tried to drive through a pond that made the Jeep look like a primordial creature crawling from the muck.

What About Low Range?

But if you don't have an Auto setting, then 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. And low range 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. A Highlander won't.

a close up of a car: The Infiniti QX80 offers three flavors of four-wheel-drive. And a handy traction-control-off button.© INFINITI The Infiniti QX80 offers three flavors of four-wheel-drive. And a handy traction-control-off button.

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.

a close up of electronics: Two important buttons in the Toyota Tacoma TRD Pro: rear diff lock and traction control off. Plus, the switch for the dome lights!© Toyota Two important buttons in the Toyota Tacoma TRD Pro: rear diff lock and traction control off. Plus, the switch for the dome lights!

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-and anyway, see: rear diff lock.

Finally, a word of advice that applies to any modern system: before you go off road, set your traction control. By which I mean, probably disable it. Some vehicles give you a knob with an easy pictogram to automatically set up your system (Land Rover's Terrain Response, Ford's Terrain Management) but a lot of the time it comes down to a single button with squiggly lines on it: your stability control defeat button.

a close up of a camera: The Ford Expedition doesn’t bother offering 4WD High. But it does have a rear diff lock and and custom electronics modes for different surfaces.© Ford The Ford Expedition doesn’t bother offering 4WD High. But it does have a rear diff lock and and custom electronics modes for different surfaces.

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 four-wheel-drive. That's because in certain circumstances, you want wheelspin and momentum. A few years ago I spent a day towing stuck drivers on a beach, and several of them didn't even really need a tow-they just needed to turn off their traction control systems. Because out on the sand, the cars (like a Subaru Crosstrek and Jeep Compass) detected wheelspin and cut power to the spinning wheels. Which, on sand, is basically all of them. Then you grind to a halt.

a yellow and black truck sitting on top of a car: True story: this little Jeep didn’t really need a tow. It just needed its stability control system turned off so it could throw some sand.© Ezra Dyer True story: this little Jeep didn’t really need a tow. It just needed its stability control system turned off so it could throw some sand.

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".

Then have fun going somewhere you might not have thought you could go.

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