Drive

Get to know your four-wheel drive, and how it works

When you want to go off the beaten path, nothing beats a “four-by-four,” a truck or SUV with four-wheel drive and a two-speed transfer case. But it’s important to know what’s happening in the vehicle so you can use the right configuration for the job.

“The two-speed system isn’t just about four-wheel drive, but a more off-road experience,” says Peter Frantzeskakis, vehicle engineering manager for Ford’s F-Series pickup trucks. “If you’re in a very aggressive situation, like really deep snow or mud, you can engage the 4Low to help you crawl out.”

A truck so equipped will have a dial or lever that gives you 2WD (two-wheel drive), 4High, and 4Low. Depending on the model, it may also have 4Auto. In 2WD, it operates only the rear wheels. In the 4WD settings, it engages the transfer case, which is the unit that transfers power to the front wheels as well.

In 4High, all four wheels receive power at the same rate as they would in 2WD. This is usually sufficient for most off-road applications, but there are times when you need even more grunt, and that’s the job of the 4Low setting. “This is a low gear that the transfer case offers,” Frantzeskakis says. “This gives more multiplication of the torque that’s available.”

Simply put, when the vehicle is in 4Low, the turning power to the wheels is increased ­— in Ford’s case, by 2.64 times — to help the truck dig in and get you out of any tough going. You’re basically exchanging speed for power, so you can only travel at slower speeds in 4Low.

The 4High and 4Low settings should only be used on gravel, mud or deep snow, not on dry roads. The transfer case turns all four wheels at the same speed, and while they can slide a little on loose surfaces, the system can bind on dry surfaces, which can cause the truck to “hop” when you turn, or potentially even damage the four-wheel system.

Vehicles with a 4Auto setting have a transfer case that can adjust power to each axle, so these can be driven in four-wheel on firm pavement. Cars and SUVs with all-wheel drive, or AWD, can also be driven on all surfaces.

Tips

  • Know your system. There are different types of AWD and 4WD, and auto manufacturers sometimes use whichever term they prefer, so be sure you know what type of system you have.

  • Tread choice. Off-road ability also depends on the tires, and you need tires with aggressive tread if you’re planning on travelling over very difficult terrain.

  • Neutral notice. Most vehicles require you to be stopped and in neutral before you can shift into 4Low.

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