Despite the increasing number of online resources and shifting dealer strategies, car shopping is still a headache. There’s a long list of confusing topics when choosing the right options, but when it comes to deciphering the difference between all-wheel drive (AWD) and four-wheel drive (4WD), it can get a little bit tricky. Often, these terms are used interchangeably, but are they really the same? Quick answer: no, they are not the same.
While they seem like they do the same thing, they are in fact very different, and the differences affect their functionality. So what’s the difference between four-wheel drive and all-wheel drive, how will each impact your daily driving life, and which badge belongs on your car?
Four-Wheel Drive (4WD)
Let’s start with “four-wheel drive.” Displayed often as 4WD and sometimes referred to as four-by-four or 4×4, this system’s main distinction is it’s typically used on vehicles designed and built to handle the unpaved wilderness. More so, four-wheel drive typically only applies to the context of vehicles designed for intended off-road applications. This includes rugged trucks and SUVs like the Jeep Wrangler, Mercedes-Benz G-Class, and the Toyota Land Cruiser.
In a nutshell, it’s a system that sends power to all four wheels equally and without vectoring (controlling the division of power delivery between the wheels or axles), meaning each wheel will spin at the same constant rate as all the others. Power simply comes from the engine and is transferred to the transmission, where a device known as a transfer case divides the power between the front and rear axles.
The equal split of power is great for maneuvering real tough and low-traction situations. But it isn’t very friendly on the road in terms of everyday driveability. When you have the four-wheel drive system functioning on the road, it can make simple actions such as turning around in a tight street very difficult. This is because wheels want to rotate at different rates whenever a vehicle makes a turn.
Most modern 4WD systems are “part-time” and at the flick of a switch four-wheel drive can be engaged
In essence, the inside wheel has to turn more slowly than the outside wheel, which is covering more ground. You might hear a rubbing noise when you approach full lock.
This is why most 4WD systems are part-time systems that can be disabled. The car operates in two-wheel drive in normal conditions to improve on-road driveability but still offers four-wheel traction when you need it.
What about “part-time” vs. “full-time”?
Here’s the difference between these commonly-used terms. Most modern 4WD systems are “part-time” where the vehicle by default is in two-wheel drive mode and at the flick of a switch or touch of a button (or yank of a center console-mounted lever on older trucks), four-wheel drive can be engaged for low-traction situations.
They also feature multiple settings for multi-geared transfer cases, such as 4-Low or 4-High. ‘High’ basically compensates for the differences in rotational rates of all four wheels whenever a vehicle turns and higher rates of speed. This limited allowance and compensation for differentiating rotational rates is called ‘limited slip’ between the inside and outside wheels. Basically, it solves the issues of driveability with no-slip four-wheel drive system where all four-wheels are spinning at the same rate.
4-High limits and vectors available power to the wheels so you can move quickly over slippery surfaces (up to about 60 mph). To get the most available power, however, you’ll want 4-Low, which means 4WD with low-range. This low-range gearbox is for low-speed maneuverability, such as rock crawling or getting unstuck, and is only for such conditions.
You really don’t want to go too fast in 4WD Low because things will start breaking, and your trip will start getting expensive.
To avoid complexity, a word of advice: you really don’t want to go too fast in 4WD Low because things will start breaking, and your trip will start getting expensive. Most newer vehicles with part-time systems have an automatic deactivation when the vehicle goes beyond a certain speed to avoid this damage, but older trucks typically do not.
Part-time four-wheel drive systems generally feature locking and unlocking differentials. Between each axle sits a differential that compensates for wheels spinning at different rates. By locking a differential at a front or rear axle, you are inhibiting any slip from occurring at the axle, forcing each wheel at said axle to turn at the same rate.
Most trucks and SUVs (even crossovers with all-wheel drive) come with center-locking differentials which send power evenly to the front and rear axles, but those axles have their own differentials which vary the amount of power between the left and right wheels depending on the amount of grip available. That’s when traction and stability control systems step in to limit actual wheel slip. But that’s a discussion for another day.
|4WD Pros||4WD Cons|
|Best traction in off-road conditions||Adds weight and complexity to cars|
|Can sometimes be turned off to improve fuel economy||Can’t be used in all conditions|
|Proven, rugged technology||More expensive than two-wheel drive models|
Some trucks, such as the Mercedes G-Class, come with three locking differentials, one in the center, and one at each axle, making it a unique example. It also explains why the G is often referred to as Germany’s Hummer.
As for full-time four-wheel drive systems, there essentially isn’t a 2WD mode, meaning the four-wheel drive system is active all the time, sending power to all four wheels at the same time but with limited-slip capabilities. This system is becoming more obsolete as technology and the part-time system makes more sense for most consumers these days. Not everyone needs four-wheel drive all the time.
Older trucks, such as 1990s Toyota Land Cruisers, have full-time systems. They come with an additional center differential to enable limited slip for better drivability on the road, and the system does it all for you
All-Wheel Drive (AWD)
All-wheel drive is a much more recent innovation and is a little more complicated. It crops up on everything from supercars like the Audi R8 to grocery-getters like the Buick Encore. But, to simplify, it’s actually very similar to the concept of part-time four-wheel drive.
Think of all-wheel drive as similar to the part-time four-wheel drive system, except for cars and some crossovers.
Where the main distinction with four-wheel drive is that the system tries to send as much power to all four wheels as equally as possible for utmost traction, all-wheel drive is all about varying the amount of power to each wheel, either by physically with differentials or transfer cases or electronically by brake vectoring (where the brakes are used to slow-down a specific wheel due to traction loss).
All-wheel drive is often associated with road-going vehicles, such as sedans, wagons, crossovers, and even some larger SUVs. Crossovers like the Honda CR-V, Toyota RAV-4, and Mazda CX-3 tend to fall under the “car” category while SUVs like the Chevrolet Tahoe and Toyota 4Runner fall under the “truck” category. Here’s our article on how to better understand the differences between crossovers and SUVs.
In a nutshell, think of all-wheel drive as similar to the part-time four-wheel drive system we just described, except for cars and some crossovers. Note also that it’s completely automated. With all-wheel drive, the system is constantly active and needs no activation or input from the driver to work. However, most newer all-wheel-drive vehicles send power to a primary axle, either the front or the rear, and sends power away from the slipping wheels when it detects a loss of traction.
Remember Subaru’s classic slogan? “Transferring power from the wheels that slip to the wheels that grip.” That’s the system in a nutshell. Some constantly send power to both axles and adjust power delivery according to which wheel loses or maintains traction.
All-wheel drive is becoming increasingly common in performance applications. The Mercedes-AMG E63 is a perfect example. It is now sold only in AWD in the United States because its 600-plus-horsepower output can overwhelm the rear wheels if they try transferring it to the pavement on their own. Even when we aren’t talking about tire-scorching performance cars, splitting power evenly means added stability in all types of weather.
All-Wheel Drive does have some clear advantages over 4WD.
AWD isn’t quite as robust as 4WD and it can’t match the acute power delivery necessary for low-speed off-roading like rock crawling. The maintenance and complexity of these systems can also get extraordinarily expensive, but ensuring it functions as intended is crucial to your safety.
All-Wheel Drive does have some clear advantages over 4WD. These days, computers are involved in most AWD systems. Sensors on each wheel monitor traction, wheel speed, and several other data points hundreds of times per second. An engine control unit (ECU) analyzes traction conditions and decides which wheel receives power. This type of system, usually called torque vectoring, appears on everything from the Subaru WRX to the Dodge Charger. Torque vectoring has allowed massive improvements in handling and all-weather capability.
Electrified all-wheel drive
Each axle gets its own electric motor so the four wheels are always powered but there’s no mechanical connection between the front and the back of the car. This improves traction and performance while helping clear up passenger space in the cabin because there’s no need for a transmission tunnel.
Some plug-in hybrid vehicles use a blend of technologies to achieve all-wheel drive. Take Volvo’s XC90 T8, for example. The 2.0-liter four-cylinder engine spins the front wheels while an electric motor mounted over the rear axle spins the rear wheels. It’s front-wheel drive when the four-cylinder works on its own, rear-wheel drive in electric-only mode, and all-wheel drive with both power sources up and running.
|AWD Pros||AWD Cons|
|Provides increased grip and control under all road conditions||Reduces fuel economy|
|Gives sportier handling and traction to a broader range of cars||Increases the weight and complexity of vehicles|
|Works all the time||Not as good in extreme off-road conditions|
Automakers are getting serious about electrified cars so these through-the-road all-wheel drive systems will become more common in the coming years.
So, which do I want?
Ultimately, the system you choose largely depends on your driving needs and where you live. Four-wheel drive is your best bet if you plan on using your vehicle off-road and in difficult terrain on a regular basis. It’s normally found on SUVs and pickup trucks that boast the durability to match the ruggedness of a four-wheel drive system. For most people, however, all-wheel drive makes more sense.
In the sort of winter road conditions most drivers experience, a modern all-wheel drive system that responds instantly without the driver’s input is all most people need. Additionally, all-wheel drive vehicles normally have a better weight distribution, which improves traction and performance.
You might not need either. If you live in an area where winter is mild at worst, you’d only benefit from having four powered wheels a couple of times a year. We recommend you keep your vehicle simple and cheap, stick to two-wheel drive, and invest in a good set of winter tires.