How Does 4WD Work? (Cars, Trucks, SUVs, and Jeeps)
4WD is becoming more and more popular on vehicles across the board, from compact coupes to full-size pickup trucks.
It helps with traction and grip by using all four wheels as drive wheels instead of just relying on the fronts or rears.
But how does it work?
How Does 4WD Work?
When 4WD is turned on, the engine is able to transmit power to all four wheels instead of just two. It does this through the transfer case and transmission, which work together to split the torque between the front and rear axles so that all four wheels turn. This offers better grip and traction.
While that’s the general premise of how four-wheel drive works, it’s not exactly the same on all types of vehicles.
So if you want to know how 4WD works in your car or truck, continue reading to learn everything you want to know.
Does 4WD work the same way in cars and trucks?
As you likely already know, a four-wheel drive (4WD) system means that all four wheels on the vehicle are spun by the drivetrain.
After all, that much is explained in the term itself.
But what you might not have noticed before is that the term 4WD is usually reserved specifically for trucks and Jeeps.
Most cars and SUVs use systems known as all-wheel drive (AWD).
These are not just interchangeable terms that describe the exact same thing.
We’ll get into the actual difference between the two systems shortly.
But first, suffice it to say that cars and trucks do not use these systems in the same ways, since they use completely different systems entirely.
Trucks, Jeeps, and some big SUVs typically use 4WD systems, which are usually made up of a series of transfer cases, differentials, and other mechanical systems to provide torque to all four wheels.
These systems can often be turned on and off manually and only used when needed.
Cars, crossovers, and smaller SUVs, however, use AWD systems that continuously provide power and torque to all four wheels.
That last paragraph might make it seem like there really isn’t too much of a difference between the two systems.
So let’s dive a little deeper so that you know exactly which one your car has and how it works.
4WD vs AWD: What’s the Difference?
For all intents and purposes, 4WD and all-wheel drive AWD systems both work by spinning on four wheels on a vehicle at the same time instead of just two.
This helps to enhance traction, put down the full power of the engine, and even provide better handling under aggressive driving.
So what’s the difference between these two systems?
Cars and SUVs with AWD systems have sophisticated transmissions and differentials that continuously deliver torque and power to all four wheels.
Modern AWD systems can automatically apportion the torque to each wheel individually to ensure smooth and predictable performance at all speeds and under all conditions.
Taking these systems a step further, many modern vehicles even have part-time AWD systems rather than continuously spinning all four wheels.
With part-time AWD, you’ll usually be driving around under 2WD conditions.
But if you start having any traction issues when the road conditions are poor, the vehicle will automatically apply torque to all four wheels to get you back on track.
4WD is a bit different from AWD and can often just be thought of as the more rugged version of the two systems.
Typically reserved for big SUVs, Jeeps, and most pickup trucks, 4WD systems usually work with a series of differentials, a transfer case, and a selector lever or knob so that you can engage the system when you want.
Most 4WD systems are built to be able to withstand more than their AWD counterparts and are ideal for the most adverse offroad conditions.
They’ll typically have a “low” and a “high” option that you can choose from depending on conditions.
In four-wheel low, you’ll get maximum traction but can’t drive as fast.
Four-wheel high is great for slippery conditions where you don’t need as much traction, and you can drive at normal speeds while this setting is engaged.
Is 4WD On All the Time?
In most cases, 4WD is not on all the time.
On trucks, SUVs, and Jeeps with 4WD systems, you can almost always select whether it’s on at all, in addition to the modes described above.
In older vehicles, there is usually a lever mounted somewhere on the floor that you can reach down and pull to engage the 4WD system, but modern vehicles have buttons and knobs that you can use instead.
With most of these systems, you can only engage four-wheel low while the vehicle is parked.
If you try to force it into low gear while you’re driving, you risk damage to the entire system.
Four-wheel high, on the other hand, can usually be turned on at any time.
Just make sure you read your owner’s manual before trying to engage it while moving!
One of the reasons that you don’t always want to have 4WD on is that it can cause issues at low speeds.
In older vehicles, engaging 4WD locks the differential so that all wheels are turned at the same speed.
At low speeds, such as when you’re parking or maneuvering around in your driveway, this can potentially damage the system if it’s a limited-slip differential since the wheels will be interlocked with one another.
AWD on the other hand usually is on at all times.
Sure, there are the part-time AWD systems described above, but most AWD systems are full-time, so they’re always engaged.
The difference is that these systems usually have the ability to apportion various amounts of torque to each wheel individually.
This means the 4WD issue just discussed is not a problem on AWD systems.
Is 4WD Better Than 2WD?
The 4WD vs 2WD debate has been going on for as long as cars and trucks have been produced.
So which one is better? For the majority of people and situations, a 4WD (or AWD) vehicle is almost always going to be a better option than 2WD.
The biggest reason is of course the increased traction and performance capabilities that a 4WD system offers.
As mentioned above, 4WD systems can almost always be turned on at will, either via a floor-mounted lever, buttons, or knobs.
This means that when you don’t have the system engaged, you are actually driving using 2WD.
So you almost have all of the benefits of 2WD while having the ability to turn on 4WD and use all four wheels for traction.
This difference is noticeable not only in actual performance but also in the price of the truck or SUV when you buy it.
Almost without fail, if you compare identical trucks side-by-side with the only difference being that one is 2WD and one is 4WD, the 4WD truck will be more expensive.
That is usually a pretty good indicator that a feature is beneficial since most people wouldn’t pay more for a lesser product.
Are There Any Downsides to Using 4WD?
So if 4WD is so much better than 2WD, why would anyone ever opt for a 2WD truck or SUV? Well, like all things, there are a couple of downsides that you should keep in mind if you’re considering a 4WD vehicle.
The first one was alluded to above — they typically cost more than a comparable 2WD vehicle.
Although this may very well be indicative that 4WD is better than 2WD, it comes at a price.
And this price might not be worth the benefits in most cases.
If you don’t plan on doing any sort of off-road driving whatsoever, then paying extra money for 4WD might not be a good choice.
Secondly, 4WD and AWD systems lead to poor gas mileage compared to vehicles that just have two drive wheels.
This is due for two main reasons. First, these systems add extra weight — up to a few hundred pounds more — to the vehicle, which lowers its gas mileage
Additionally, the engine must work harder because it has to power all four wheels, which reduces its efficiency.
So there are pros and cons to keep in mind next time you’re in the market for a new car, truck, Jeep, or SUV.
Enhanced traction, grip, and handling are undoubtedly great bonuses.
That said, it comes at a cost in terms of the purchase price and fuel efficiency.
But now that you know how 4WD and AWD systems work and what they can do for you, you’ll be able to make an informed decision next time you’re in the market.