AWD and 4WD can help you cover rough terrain with confidence.
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At one time, if you wanted a vehicle with four driven wheels, you were limited to just a handful of large trucks and full-size SUVs, most of which were used for work chores or off-road adventure. But times have changed. Now, many vehicles sold in the U.S. are available with either all-wheel drive (AWD) or four-wheel drive (4WD), making them more capable and more desirable to a wider audience.
But what's the difference between AWD and 4WD? And which is right for you? The AWD vs. 4WD terminology can sometimes be confusing, especially since AWD systems have become more robust and 4WD has gotten more sophisticated, blurring the distinction between the two. Adding to the confusion, various manufacturers often use these terms differently.
Here's how each system works and the advantages and disadvantages of each. With this knowledge, you can make an informed decision when shopping for your next family SUV, midsize SUV, car, or truck.
What Is All-Wheel Drive?
All-wheel-drive vehicles use, as the name suggests, systems that power the front and rear wheels. There are two kinds of all-wheel-drive systems worth pointing out. The first system is called all-time of full-time AWD. It drives all four wheels continuously. The second system, referred to as a part-time all-wheel-drive or an automatic AWD system, only uses AWD when necessary. Most of the time, these part-time systems are in two-wheel-drive mode (which can conserve fuel), switching to AWD only when traction is needed.
How Does All-Wheel Drive Work?
AWD systems, both full-time and part-time, generally operate with no input from the driver, although some offer selectable modes that allow a degree of control over how much power goes where. All the wheels get torque through a series of differentials, viscous couplings, and/or multi-plate clutches, which help distribute power to the wheels so that the car's traction is optimized. The vehicle still operates smoothly under routine conditions.
In full-time AWD, both the front and rear axles are driven all the time. On dry pavement, this kind of AWD can help the vehicle handle better and ensure that full power gets to the road. And in slippery conditions, such as ice, snow, or mud, it provides additional traction for more consistent traction and more confident handling.
In usual operation, part-time AWD sends torque to two driven wheels, either the front or rear, depending on the make and model. The system then automatically engages the other two wheels when road conditions demand extra traction. Modern part-time AWD systems use an array of electronic sensors that feed information to a computer, which controls the amount of power directed to each wheel.
All-Wheel-Drive Pros and Cons
The best thing about AWD is that the driver doesn't have to make any decisions about engaging the system. Either all the wheels are being driven full time or the system is designed to sense loss of traction and send power where it's needed. AWD is available on a wide variety of vehicles, from compact sedans to performance models to all sizes of SUVs, giving you a broad range of choices.
While AWD is able to work well in a range of conditions, from rain to snow to light off-roading, it's generally considered a lesser choice by serious off-roaders. This perception is changing somewhat as modern AWD systems improve their capabilities, but many drivers who like to venture far off the beaten path still prefer to decide for themselves when to engage four-wheel drive. AWD also usually increases the cost of a vehicle and in most cases reduces fuel economy.
What Is Four-Wheel Drive?
More likely to be found in pickup trucks and large SUV's, four-wheel-drive is a more traditional system for driving all four wheels. If you think of something crawling over rocks, off-roading through the desert, or crossing a river with water up to the mirrors - that's probably a vehicle with 4WD.
Generally driven by a mechanical connection, 4WD systems use a series of front, center, and rear differentials, along with transfer cases and couplings to provide torque to all four wheels. These systems have become more sophisticated over the years, allowing for the connection and disconnection of 4WD via buttons and knobs, but many traditional 4WD systems are managed through a floor-mounted lever that looks like a second gear shifter.
How Does Four-Wheel Drive Work?
Like AWD systems, 4WD is designed to send torque to all four of a vehicle's wheels to increase traction when needed. But 4WD systems tend to be more robust than AWD ones and can generally handle more rugged terrain. And they too come in two types: full-time and part-time.
Many 4WD systems also have low and high ranges that can be selected by the driver, either with an electronic switch or a floor-mounted mechanical lever. The low setting provides maximum traction in an off-road environment, while the high setting is useful for slippery on-road conditions, such as packed snow, ice, loose sand, or gravel.
Full-Time Four-Wheel Drive
Full-time 4WD operates as a full-time AWD system does, with all four wheels receiving power on a continuous basis. In some designs, the driver may have the option of controlling how power is apportioned to the front and rear axles through selectable modes.
Part-Time Four-Wheel Drive
This type of system is the real traditionalist of four-wheel propulsion and can most often be found in trucks and SUVs that are designed to work and play in more extreme conditions. In this case, the vehicle is typically driven by two wheels, most often in the rear. The driver needs to make the decision to engage 4WD when needed and either push a button or shift a lever. Some systems also allow the driver to lock the vehicle's differentials for extra traction in extreme off-road conditions.
Four-Wheel-Drive Pros and Cons
4WD vehicles are generally best at handling adverse conditions, both on road and off. Even though these systems are now available in well-appointed luxury trucks and SUVs, at their heart they tend to be designed for ruggedness and maximum pulling power, and they are well suited for work and play in difficult terrain.
These days, 4WD design has become increasingly refined, as has the design of the vehicles that have with available. But depending on the make and model, 4WD is often paired with a heavy-duty suspension, resulting in a stiffer ride than you'd get in a 2WD or AWD vehicle. These systems can also take a toll on fuel economy and can increase the initial cost of the vehicle.
4WD vs. AWD in Snow
Whether you have four-wheel-drive, all-wheel-drive, or you're running around in studded cleats, you can always lose traction if you go beyond the limits of grip. Your tires, your speed, and especially the road conditions are all a big part of maintaining traction. And, regardless of what kind of drive system you have, braking distances are increased in wet or snowy conditions. Thankfully, a vehicle with AWD or 4WD can give you an advantage in snowy or icy conditions, especially when it comes to establishing traction. The extra cost of a 4WD/AWD is certainly worth considering depending on how you use your vehicle and where you live.
Colder climates, especially those with hard-packed snow or ice, are more likely to see rapidly changing road conditions. For these kinds of conditions, AWD systems which can automatically engage four-wheel torque, are best. Many modern AWD systems will allow you to select a "snow" or "low traction" mode based on the road condition, but even systems left in "automatic" or default mode can act more quickly than the driver can.
If you're navigating deep snow or more extreme conditions, 4WD is better. Icy hills and big snow drifts will be difficult for AWD systems and 4WD systems will get you unstuck more easily.
Do You Need AWD or 4WD?
Where you live and the kind of road conditions you encounter on a daily basis should be the main factor in whether you buy a vehicle with 4WD or AWD. Personal preference figures into the equation too.
Cars, trucks and SUVs of all sizes are available with all-wheel-drive. This means you have a wide range of vehicles to choose from if you go with AWD. These vehicles will provide increased traction during typical winter road conditions and, depending on the vehicle, they may even be up for a bit of light off-roading. These vehicles are great all-arounders and make the fewer compromises in terms of ride quality and fuel economy while providing power to all four wheels.
A vehicle with 4WD is likely to make a few compromises in terms of ride quality and fuel economy, but it's a great choice for buyers who live in remote areas. If you encounter extreme weather on a regular basis or you enjoy challenging off-road adventures, 4WD is the right system for you. Vehicles equipped with 4WD are more likely to have higher ground clearance, which will help them manage deep snow, steep grades and rocky terrain. And, if you're looking for added driver control over how the power is delivered, vehicles with part-time 4WD and low- and high-range features are probably the choice for you.