Shannon Love Professional Auto Consultant
big debate on 4WD or AWD
What is better -- 4WD, AWD 2WD, FWD, and or traction control?
Modern SUVs, pickups, minivans, and wagons offer a number of drive-train systems designed to help out in slippery conditions, including four-wheel drive, all-wheel drive, and traction control. What's the difference?
|4WD includes low-range gearing that helps a vehicle tackle deep mud or snow as well as more-challenging off-road conditions, such as climbing over rocky terrain or descending steep hills. The vehicle must be stopped or slowed to a crawl to shift in or out of low range, which is done with either a lever or a switch..|
|AWD has become almost as common as 4WD. AWD lacks the low-range gearing of a 4WD system, but still provides all the traction that's needed for the types of slippery conditions that drivers typically encounter, including inclement weather road conditions and light off-roading. In fact, a vehicle's off-road capabilities are often more limited by ground clearance than by AWD. All AWD systems are full-time, which means you never have to shift between AWD and 2WD modes.|
|Traction control is a lighter,
less-expensive alternative to 4WD and AWD, and is used by many
two-wheel-drive vehicles to provide maximum traction at the drive
wheels. If the system detects one drive wheel slipping, it automatically
applies a slight amount of brake pressure to that wheel and, if
necessary, cuts back engine power. That instantaneously stops the
slipping and sends power to the drive wheel with the most grip. In many
conditions, this provides sufficient traction, although if neither drive
wheel has grip, traction-control won't help.
Which system is best for you depends on what type of conditions you'll be driving in and how much you want to pay. For rain and light snow, either traction control or AWD will work well, although AWD will give you a greater margin of safety. AWD will also be fine for most normal snow conditions on paved or graded roads, or for traveling on forest, desert, or other dirt roads without high rocks, deep sand, or steep inclines. If going well off the beaten track, or where you'll likely encounter more severe conditions is most important, you'll probably be better off opting for 4WD.
Permanent 4WD or AWD.
this full-time system, found on SUVs and cars, the vehicle is constantly
providing power to all four wheels, usually with power being shifted
between the front and rear axles as needed. The advantages are that the
vehicle always provides maximum traction in both dry and slippery
conditions. As with all full-time systems, it requires no action from
For maximum traction, the center differential can usually be locked, which distributes power evenly to all four wheels. In some systems this is done automatically, while in others the driver must manually lock it.
|Automatic 4WD or AWD.|
|.Available on various SUVs, this type of full-time system lets the vehicle operate in 2WD (either front or rear, depending on the model) until the system judges that 4WD or AWD is needed. It then automatically routes power to all four wheels, varying the ratio between front and rear axles as necessary. In most systems, that is detected by a slipping wheel. More-sophisticated systems use software that switches the system to 4WD or AWD during specific driving conditions--before a wheel begins to slip. Automatic systems provide the key advantages|
Found on some SUVs, this type of system allows the driver to select between several modes, including 2WD, a permanent or automatic 4WD mode, and, on some vehicles, a part-time 4WD mode designed to provide more traction.
|Found on SUVs and pickups, this basic type requires the driver to manually shift between 2WD and 4WD using either a lever or a switch. All current systems allow you to "shift on the fly" (or shift between modes while driving). Vehicles with part-time systems, though, aren't designed to be driven on dry pavement when in 4WD mode.|
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