The Advantages of 4x4 vs. AWD
The advantage of a 4X4, or four-wheel drive, over all-wheel drive is that drivers can operate a 4X4 in rough terrain. All-wheel drive vehicles are for paved roads and don’t respond well to off-road conditions. Truck, car or sport-utility vehicle buyers should consider the different types of four- and all-wheel-drive models and determine which vehicle suits their needs. There are full- and part-time 4X4s, and full-time and automatic, or “on-demand,” AWDs.
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Part-Time 4X4
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The term 4X4 no longer adequately describes a contemporary four-wheel drive car. Contemporary vehicles feature full- and part-time four-wheel drives and all-wheel drives that are either full-time or apply only when driving circumstances require it. All-wheel drive is a safety and stability feature. Automobile literature and dealers may confuse the terms by selling AWDs as four-wheel drives even if these vehicles don’t perform in rough terrain. Without making the distinction, a buyer may purchase a vehicle for the wrong reasons. Older SUVs such as the Willys, International-Harvester Scouts and Jeep Wranglers feature part-time four-wheel drives. Drivers did not engage four-wheel drive on paved roads but only shifted into four-wheel drive for off-road use. The transmission settings were 2WD, Hi 4WD, Lo 4WD. The Low 4WD gear is essential for navigating rough terrain, making the vehicle an excellent off-road candidate.
Full-Time 4X4
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Land Rovers, Range Rovers, some earlier Mercedes-Benz M-Class and other luxury SUVS may be equipped with full-time 4WD. This system gives vehicles more versatility to handle paved and unpaved roads with more traction. When equipped with axle differential locks, vehicles equipped with full-time 4WD handle exceptionally well in adverse road conditions. There is only Hi 4WD and Lo 4WD. The disadvantage is all four wheels are always powered, whether you need it or not.
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Full-Time AWD
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All-wheel drive essentially gives the driver better traction and stability on paved roads. Subarus, late-model Mercedes-Benz M-Class and the Audi Quattro use AWD. Like the full-time 4X4, the AWD’s wheels are powered at all times. However, AWD vehicles are poor candidates for off-road use, because they lack a two-speed transfer case that allows the vehicle to shift into a lower gear to create torque at slow speeds.
On-Demand AWD
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On-demand or automatic AWD vehicles are essentially two-wheel-drive cars or SUVs that occasionally, even rarely, engage all four wheels simultaneously. The AWD vehicle employs only two-wheel drive under normal driving conditions and on paved roads. If driving conditions change, such as rain that slicks the road or a snowstorm, the AWD temporarily powers all four wheels. One axle provides torque to the wheels, but if the wheels lose traction, the second axle kicks in to deliver traction to compensate for the other axle’s loss. Once the primary axle regains traction, the second axle shuts off and the vehicle returns to two-wheel drive. Honda CRVs and late-model Toyota RAV4s use automatic AWD. These vehicles are not suitable for off-road driving. Buyers should be mindful that on-demand AWD is not the same as part-time 4WD and is not for use off of paved roads.
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