What Does AWD Mean in Cars?

by Richard Rowe

All Wheel Drive (AWD) is one of those things that everyone knows they should want, but don't exactly know what it is. This term is often confused with the similar Four Wheel Drive (4WD), but the systems differ greatly.

Purpose

All wheel drive is a type of four-wheel drive system, and is used to give a car more traction for cornering and all-weather safety. AWD is generally not designed for hard-core off-roading.

AWD vs. 4WD

A 4WD system uses a transfer case to engage the front and rear axles, locking them together. AWD uses a center differential (similar to those found in the axles) in place of the 4WD's transfer case to allow the front and rear axles to turn at different speeds.

Power Variation

Whereas a 4WD system is permanently locked at a 50/50 front/rear power split, an AWD system can vary the amount of power sent to the front or rear, depending on road conditions and wheel-slip sensed by the computer.

Power Split

Most AWD systems send power to the front wheels under normal conditions, and only engage the rear axle when slip is detected.

Performance Systems

Performance-oriented AWD systems often bias their power split to the rear and engage the front tires as little as possible to maintain traction.

About the Author

Richard Rowe has been writing professionally since 2007, specializing in automotive topics. He has worked as a tractor-trailer driver and mechanic, a rigger at a fire engine factory and as a race-car driver and builder. Rowe studied engineering, philosophy and American literature at Central Florida Community College.

Photo Credits

  • photo_camera Image by Flickr.com, courtesy of Alex Steffler