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 Gelandewagen, 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 unique device known as a transfer case divides the power between the front and rear axles.
This 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 very difficult. This is because wheels want to rotate at different rates whenever a vehicle makes a turn. In essence, the inside wheel has to turn more slowly than the outside wheel, which is covering more ground.
This is why most 4WD systems are part-time systems and can be disabled for two-wheel drive to improve on-road driveability and extra four-wheel traction when you need it.
What about “part-time” vs. “full-time”?
You may have heard of these terms. So here’s the difference. 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. To avoid complexity, a word of advice: you really don’t want to go too fast in 4WD Low because things will start breaking. 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.
Most “part-time four-wheel drive systems” also 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.
Some trucks, such as the Mercedes-Benz Gelandewagen, come with three locking differentials, one in the center, and one at each axle, making it a unique example. It also explains why the Gelandewagen 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.
|4WD Pros||4WD Cons|
|Best traction in off-road conditions||Adds weight and complexity to cars|
|Can be turned off to improve fuel economy||Can’t be used in all conditions|
|Proven, rugged technology||More expensive than two wheel drive models|
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.
Where the main distinction with four-wheel drive (4WD) is that the system tries to send as much power to all four wheels as equally as possible for utmost traction, all-wheel drive (AWD) is all about varying the amount of power to each wheel, either by physically (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, crossover SUVs, and even some larger SUVs today. Trucks as aforementioned have four-wheel drive systems. 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 crossover SUVs, and 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 for front-wheel-drive-based all-wheel-drive systems (like Subarus and the crossovers previously mentioned), or to the rear for rear-wheel-drive-based systems (like BMW’s xDrive or Mercedes-Benz’s 4MATIC).
And whenever the vehicle’s systems sense a loss of traction, it will electronically and physically divert power away from the slipping wheels to the wheels with traction. (remember Subaru’s classic slogan for its all-wheel system, ‘transferring power from the wheels that slip to the wheels that grip’).
Some constantly send power to both axles and all-four wheels, and adjust power delivery according to which wheel loses or maintains traction.
All-wheel drive has also been on the increase in performance applications. The Mercedes-AMG E63 is a perfect example. It is now sold only in AWD in the United States because its massive power reserves of over 500 horsepower can overwhelm the traction of the rear wheels alone. Even when we aren’t talking about tire-scorching performance cars, splitting power evenly means added stability in all types of weather.
AWD isn’t quite as robust as 4WD and it can’t match the acute power delivery necessary for low-speed off-roading (i.e. rock crawling). The maintenance and complexity of these systems can also get extraordinarily expensive, but ensuring its function is crucial to your safety.
AWD 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 a second. An ECU (engine control unit) dictates where power is sent and to which individual wheel depending on whichever has the most grip.
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.
AWD for EVs
But wait, there’s more. Electrified powertrains add another option when it comes to AWD systems, namely the ability to use an electric motor to power a set of wheels with two axles in tandem without any mechanical connection to the other set. For example, Tesla’s Model S can come with all-wheel drive, where two electric motors power each axle, versus the rear-wheel drive version with one electric motor at the back.
In hybrids and plug-in hybrids, an internal-combustion engine can be used to power one set of wheels, while an electric motor powers the other. This is called “through-the-road” AWD, and it’s currently used on vehicles such as the Volvo XC90 T8 plug-in hybrid and the Toyota RAV4 Hybrid.
As more automakers get serious about electrified cars, it’s possible that these AWD systems will become more common. Given the current popularity of SUVs and crossovers, automakers will have to offer AWD in order to take hybrids, plug-in hybrids, and electric cars into the mainstream.
|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|
So, which do I want?
As the pros and cons show, your four-wheel drive decision depends on your driving needs. If you plan on using your vehicle off-road and in difficult terrain often, 4WD is definitely your best bet. 4WD appears on pickups and truck-platform SUVs that have the durability to match the ruggedness of a 4WD system. For most people, however, AWD makes more sense.
In the sort of winter road conditions that most drivers experience, a modern all-wheel drive system that responds instantly without the driver having to toggle any switches is all most people need. In addition, AWD vehicles tend to have better weight distribution, which improves traction and performance.
The reality is that for many drivers, you don’t need either. If you live in an area that doesn’t get real wintery weather, you probably would only notice the difference a couple of times a year, and in many cases, a good set of winter tires will make the biggest difference. Seriously. Tires can do far more than AWD or 4WD will on all-season or summer rubber.