If like many people you thought four-wheel drive and all-wheel drive were the same things, then you might be surprised to learn that they are in fact very different systems that have quite a significant impact on the vehicle they are implemented on.
But, AWD Vs 4WD: What is the difference? Which is better: AWD vs 4WD? Is AWD the same as 4WD? People have a lot of questions about whether AWD or 4WD is better for their daily drive. AWD and 4WD are similar, yet have a few key differences that you’ll need to know if you truly want to drive informed. Read on.
What Is All-Wheel Drive?
All-Wheel Drive or AWD refers to a system that allows all four wheels to gain traction independently. The difference between AWD and 4WD is that AWD is usually always on while you have the option to toggle between 4WD on and off. 4WD is an addition you’ll usually find on a truck, while AWD is more suited to cars and SUVs.
All-wheel drive is added to a car by getting three differentials or gears in different parts of the car. You’ll find the three gears box at the front, center, and rear of your car, and these differentials ensure that your four tires receive traction independently, allowing for superior traction and handling in all types of weather conditions.
There are two types of all-wheel drive systems worth pointing out. The first system is called all-time or full-time AWD. It drives all four wheels continuously. The second system, called the part-time all-wheel drive or automatic AWD system, uses AWD only when needed.
Most often, these part-time systems are in two-wheel drive mode (which can save fuel) and only switch to AWD when traction is needed.
How Does All-Wheel Drive Work?
AWD systems, both full-time and part-time, generally operate without driver input, although some offer selectable modes that allow a degree of control over how much power goes where.
All wheels receive torque through a series of differentials, viscous couplings, and/or multi-plate clutches that help distribute power to the wheels, optimizing the vehicle’s traction. The vehicle still runs smoothly under everyday conditions.
Full-Time AWD
In the full-time AWD, both the front and rear axles are constantly driven. On a dry road, such an all-wheel drive can help the vehicle to handle better and ensure that the full power comes onto the road. And in slippery conditions like ice, snow, or mud, it provides extra traction for smoother traction and more confident handling.
Part-Time AWD
Part-time AWD sends torque to two driven wheels, either front or rear, depending on make and model. The system then automatically engages the other two wheels when road conditions call for additional traction.
Modern part-time AWD systems use an array of electronic sensors that relay information to a computer that controls the amount of power directed to each wheel. Another vehicle segment gaining traction is AWD hybrid cars, which combine fuel economy with all-weather capability.
AWD Pros
- Added traction in bad weather
- Operates automatically and seamlessly
- System reaction is quicker than a human’s
- More fuel-efficient than 4WD
- Added value if you sell
AWD Cons
- Cost
- Not engineered for more extreme situations
What is Four-wheel drive?
Four-wheel drive or 4WD is the more traditional system that comes to mind for most people when they think of powertrains that drive all four wheels of a vehicle. No wonder, since the principle goes back almost to the beginnings of motorized transportation.
The stereotypical image of a 4WD vehicle is that of a truck with high ground clearance, a shielded underbody, tow hooks, and large knobby tires. In fact, this system is mainly found in trucks and SUVs.
But over the years 4WD technology has become more sophisticated and while generally suited to more serious off-road use, it can now be found in a wider range of comfortable, even luxurious models.
4WD systems deliver torque through a series of the front, rear, and center differentials, transfer cases, and couplings, that allow the vehicle to operate with maximum traction in a variety of conditions.
How 4-Wheel Drive Work?
Not always, but most commonly, 4WD is a part-time system. Various automakers take different paths to power all four wheels, as we’ve already pointed out. But for the sake of keeping things simple, most 4WD systems work part-time.
Unlike AWD systems, relying on a computer to shift engine output to all four wheels, 4WD systems require some driver participation to get the most performance out of all the wheels. This means that by way of a button, dial, or shift lever, the driver must engage the system at some point. A true 4WD system should never be engaged on dry pavement.
It’s not wise to use 4WD on anything but slippery, loose, or rugged surfaces because both axles lock together, with all four wheels rotating at exactly the same speed. This isn’t much of an issue when traveling in a straight line on dry pavement. However, in turning the vehicle, the outside wheels must turn faster than the inside wheels.
This creates a situation where, in 4WD, the wheels on one side of the vehicle fight the wheels on the other side. This puts a lot of stress on the system. It’s a sure way to cause damage. On slippery or loose (gravel) surfaces, though, all four wheels are free to slide and travel their own arcs through a curve without stress.
Let’s pause a moment and define the gear settings in a vehicle with 4WD.
- 2WD or 2-Hi is the normal mode for dry pavement. In 2-Hi, a vehicle functions as a rear-wheel-drive (RWD) vehicle.
- 4-Hi brings all four wheels to bear, locking the axles together with a fairly even split of engine power to each.
- 4-Low or 4-Lo usually requires you to bring the vehicle to a full stop to make the transition from 4-Hi. This is the gear for extreme conditions. 4-Low gearing generates more torque for difficult, low-speed situations.
There are some higher-end 4WD systems with an automatic setting for 4-Hi. The system is engineered to allow the outside and inside wheels to rotate at different speeds when in 4-Hi. These 4WD systems then function like an AWD system most of the time.
When conditions become too extreme for 4-Hi, the driver must take charge and manually shift into 4-Low.
4WD Pros
- Off-roading capability
- More towing capability than AWD
- The extra weight of 4WD contributes to improved traction
4WD Cons
- Poor fuel economy
- Can’t safely operate on dry pavement
- Additional weight increases stopping distances
How Is 4WD Different From AWD?
4WD is similar to AWD in that it provides power to two axles or all four wheels, but does so with what’s called a transfer case and can be used on-demand. In trucks and off-road vehicles like Jeep Wranglers, 4WD is a mode you can select, sometimes with a gearshift.
When it’s selected, there’s a separate range of gears for driving all four wheels, usually denoted with “Low” or “High” selections, indicating low or high gears. There are two kinds of transfer cases, chain-driven or gear-driven.
While chain-driven transfer cases are lighter, gear-driven are more durable. 4WD is great for trucks because using all four wheels makes the fuel efficiency worse, so being able to turn it off and on at will helps a great deal, whereas with AWD you wouldn’t have a choice.
What’s Best on Snow and Ice: AWD vs. 4WD
AWD is fine for most normal snow conditions or for light-duty, off-pavement excursions on dirt roads or slippery surfaces. If you’ll be driving in severe snow or true off-road situations, or if you’re interested in pursuing off-roading as a hobby, you should opt for a vehicle with 4WD and lots of ground clearance.
Keep in mind that both AWD and 4WD systems add considerable weight to a vehicle, compromising fuel economy.
With cold weather comes rapidly changing road surfaces, During the winter months, ice and snow can take over the roads, making roads especially slippery. So, to drive on these slippery surfaces, traction is crucial.
All-wheel-drive systems deliver power to all four wheels at the same time, or they automatically engage torque to all four wheels when needed. That’s why the all-wheel drive is best for driving on snowy and icy roads. With all-wheel drive, the driver does not have to use guesswork.
Meanwhile, four-wheel drive is a solid option for driving in deeper snow or more extreme winter weather conditions. For example, if you were to encounter a snowdrift or an icy hill, four-wheel drive may be better at handling these conditions.
Instead of thinking about all-wheel drive and four-wheel drive as competitors, consider which is better for your needs. ‘Where does your tire meet the snow when driving?’ If you live on a back road that isn’t plowed frequently, four-wheel drive may make more sense for your needs. Whereas, the all-wheel-drive may be a better choice for you if you live in a city where roads are plowed frequently but conditions are still slick.