What’s The Difference Between AWD and 4WD?Nov 12nd, 2019
Shopping for a new car is fraught with many difficult decisions but for the purposes of this article there’s only one decision that matters; Should I pick a Four-Wheel Drive system or an All-Wheel Drive System?
Four Wheel Drive
Four-Wheel Drive works by redirecting torque to all four wheels simultaneously, which enables the vehicle to power through loosely packed terrain with relative ease. A key point of sale for Four-Wheel Drive systems is that they tend to be more capable when it comes to rough terrain when compared to All-Wheel Drive systems. However, over time that gap has been steadily closed, albeit slowly by ever more advanced All-Wheel Drive systems. Generally speaking; Four-Wheel Drive has two power levels that dictate how the system performs:
- 4WD Low: Provides the maximum amount of low-end torque and traction. This is intended to get you out of all but the most demanding of off-roading situations. If you can’t get a vehicle moving on low then you’re not going anywhere.
- 4WD High: This is considered by some to be the standard Four-Wheel Drive setting and is most useful on slippery roads such as those covered by ice or those made up of loosely packed gravel.
All Wheel Drive
All-Wheel Drive, much like Four-Wheel Drive directs torque to all of a vehicle’s wheels to increase traction. The main difference between the two systems is that All-Wheel Drive does not require the driver to make a conscious decision to engage it because the system is always ready and able to stop you from sliding off the road. Much like Four-Wheel Drive; All-Wheel Drive comes in two different varieties.
- Full-Time: This mode sends equal amounts of power to all wheels on both of the axles and is most useful for dealing with a sudden loss of traction while driving down the road, such as when you hit an unexpected ice patch. One downside is that the additional power being constantly allocated to all four wheels means that fuel economy will be reduced; this has also become less of an issue as AWD systems have evolved.
- Part-Time: When no slippage is detected this system functions largely the same as a standard two-wheel drive does with only a single axle receiving power; which has the benefit of improved fuel economy when compared to full-time systems. The only time the vehicle will enter true AWD mode is when your vehicle sensors detect the slippage of multiple wheels at which point the system will reallocate power to compensate for any loss of traction.
It’s important to note that different manufacturers handle AWD behaviour in their vehicles differently. Many vehicles are completely automated in how they swap between drive modes. Others give the driver the option of selecting between high and low modes as they deem necessary.
Choosing which drive system you want on a vehicle really depends on what kind of driving you are planning on doing: Are you planning on using the vehicle as a daily commuter? Or are you planning on heading out into the wilderness on a regular basis? A safe metric would be to assume that if you expect to be on maintained roads 75% of the time All-Wheel Drive is a better choice. If you are planning on off-roading or using the vehicle for work on unimproved terrain then Four-Wheel Drive is probably your safest bet.