As the name implies, all-wheel drive (AWD) can feed power to each corner. Depending on the design of the system, AWD can provide maximum forward traction during acceleration. “AWD as found on many small crossover SUVs and some cars is great for those who need increased traction for mild slippery conditions such as snow, ice, or dirt trails,” Knizek says. Most AWD systems deliver power primarily to one set of wheels, front or rear. When slippage is detected at one axle, power is diverted to the other axle, in hopes of finding more traction there.
Sophisticated clutch systems and, more recently, the use of electric motors allow for precise control over the power sent to each wheel. High-performance vehicles with AWD often send power to each corner at all times. But they can alter the balance among the wheels depending on conditions or drive mode to change the car’s performance characteristics.
Not all AWD systems are equal. Subaru’s mechanical AWD system always directs at least some of the engine’s power to all four wheels, and it can direct a larger amount aft if needed. Many other systems fitted to FWD vehicles operate with 100 percent of the power normally going to the front wheels; the rear wheels then receive power only when the front wheels start slipping, or proactively based on the vehicle conditions or drive mode selection. Some performance cars that have an AWD system added to a typically RWD drivetrain send more power to the rear wheels by default for a more engaging driving experience, and only send more power to the front when needed for better traction. This transfer of power is traditionally achieved with a mechanical driveshaft running the length of the car, but electric vehicles and some hybrids utilize individual motors at each axle with no physical connection between them.
AWD systems are especially helpful in rapidly changing conditions or when driving on a road with intermittent snow and ice. It is commonly used for car-based SUVs, as well as certain cars and minivans.
