The Difference Between AWD and 4WD
The difference between the 4WD and AWD used to be clearer:
- 4WD always distributes an equal amount of power to all wheels.
- AWD distributes the power as needed, and can even run in two-wheel drive mode.
The AWD system has a differential between the front and rear wheels, while that isnít the case with 4WD. Thatís why itís recommended to turn off the 4WD when driving on dry asphalt, as it just wears out the tires and decreases MPG.
However, through the improvements in technology and especially marketing, the definitions have been completely blended and the two terms can be used interchangeably. In fact, there are several other names for this type of powertrain:
- Quattro (Italian for four) - used by Audi.
- 4Matic - used by Mercedes.
- 4Motion - used by Volkswagen.
- 4x4 (four by four) - popular with SUV manufacturers.
The real difference between 4WD and AWD can be seen only on non-conventional vehicles, like the Mercedes 6x6, military trucks, 6-wheel UTVs, and so on. Whereas 4WD literally means four powered wheels, vehicles with more than two axles can only have AWD, as itís not restricted by the number of wheels.
To give you the most accurate information possible, rather than discuss the ambiguous differences between AWD and 4WD, weíll talk about what technology works best when thereís snow on the road.
Whether youíre driving a front or rear-wheel-drive car, or an SUV with 4x4, tires are the most important factor in vehicle stability. Summer tires will stiffen due to the cold, and even if they have a large thread, they wonít be able to break as effectively.
Winter tires are made out of softer rubber, have tread patterns designed for use in snowy and icy conditions, and have more grip overall. When the temperature drops, even if the roads are dry, winter tires will perform much better.
Dealing with snowy roads is all about finesse, not pure power. A good traction system can automatically detect when wheels are losing grip, and either send more power to it or compensate through the rest. Itís typically a part of what would be considered an AWD system.
All AWD vehicles should have a variable power transfer, which in some ways is similar to traction control. Rather than power all the wheels equally at all times, an all-wheel-drive system will adjust power as needed for optimal performance.
Iíve used the AWD term here because most manufacturers label a four-wheel powertrain system with variable power as such. However, you should always check the specifications to make sure thatís the case.
Transfer Case with Reduction Gears
A low-gear transfer case isnít necessary for any kind of asphalt driving, but if you need to, or want to go off-road during winter, reduced gears will make it much easier to traverse the snow.
This type of transmission significantly lowers the rotation speed of the wheels and brings the vehicle to a crawl, while the power output of the engine remains the same. This translates to much more torque and far better control in the off-road conditions, even when itís snowy.
Marketing terms aside, AWD is generally considered better for driving in snowy weather because of the improved power distribution and traction control. For the most extreme conditions, a set of oversized all-terrain tires and gear reduction will be more than capable of delivering traction, power, and control.