All-Wheel Drive or 4-Wheel Drive? What's the Difference?

All-Wheel Drive or 4-Wheel Drive? What's the Difference?

All-wheel drive versus four-wheel drive - is there any difference? With either system, your car's transmission can send power to all four wheels. However, when it comes to both form and function, these two systems are strikingly different.

What Is Four-Wheel Drive?

Four-wheel drive is most often found on big, trail-friendly vehicles like pickup trucks and SUVs. On a four-wheel-drive vehicle, both wheel axles have a differential - a front and rear differential, respectively. Differentials are what allow two wheels on the same axle to rotate at different speeds. Driveshafts connect each differential to a transfer case, which sends engine power to both axles.

Who Needs Four-Wheel Drive?

Notably, most four-wheel-drive trucks and SUVs come with part-time four-wheel-drive technology, with default rear-wheel-drive performance. When you decide to take performance up a notch and send power to all four wheels, you can choose between two transfer-case gears: low and high. In high gear, your four-wheel-drive truck or SUV increases traction on wet or icy roads, so you can navigate dangerous conditions in optimal safety.

Of course, the real reason most drivers crave four-wheel drive is because they want to travel into rugged, off-road territory. To roll through boulder fields and muddy riverbanks with precision, just put your four-wheel drive in low gear. This setting increases traction as you slowly make your way through difficult terrain.

4 Wheel Drive vs All Wheel Drive

What Is All-Wheel Drive?

Technically, all-wheel-drive technology is simpler. Instead of a transfer case connected to two differentials, all-wheel-drive vehicles use a center differential for both axles. This center differential acts similarly to the differential on a drive axle, sending power without any control over range or speed. Unlike the low-speed transfer case in a four-wheel-drive truck, the center differential leaves lets the engine and transmission dictate speed and range.

A computer connected to the engine, transmission, throttle, and axle hubs controls the all-wheel-drive system. The computer is designed to detect slippage and transmit power to the axle that requires extra torque. Although there are some full-time all-wheel-drive systems out there, such those as in Subarus, modern all-wheel drive systems are generally found in front-wheel-drive vehicles, and typically only send power to the rear axle when the computer detects slippage.

What Are the Benefits of All-Wheel Drive?

If four-wheel drive is an all-terrain wildcat, all-wheel drive is its domesticated house cat cousin. This technology won't take you into up a mountain or far from well-trod campsite trails, but it does maximize traction - and therefore safety - for drivers who frequently travel on wet or icy roads.