‘4WD’ VS ‘AWD’: What Are the Differences?
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. Here are the key differences between four-wheel drive and all-wheel drive. Read on.
Four-Wheel Drive (4WD)
Four-wheel drive, also called 4x4 (“four by four”) or 4WD, is a system that is mainly used on vehicles manufactured to deal with rugged adventures and crawling through mud and muck. This includes pick-up trucks and SUVs like the Ford Ranger, Mercedes-Benz G-Class and the Toyota Land Cruiser.
To put it briefly, it provides torque to all of its wheels simultaneously and as quickly as possible for maximum traction. Because the power is equally divided between the two sets of wheels (front and rear), it means your vehicle is more likely to have better traction or grip in wet conditions. However, this can be dangerous once back on dry tarmac surfaces, where axles (a central shaft for a rotating wheel or gear) aren’t designed to rotate at a constant speed. In normal cornering, for example, inside wheels have to cover a smaller radius compared to the outer wheels, so if the axles are locked together, a vehicle can easily drive away with understeer in a corner. A device called the transfer case divides and redirects power from the engine to the front and rear wheels.
In order to activate a four-wheel drive system, the driver has to push a button or pull a lever to engage it. Despite four-wheel drives being extremely good for off-road driving, it isn’t designed to be activated all the time, so you have to know when are the best times to turn it on and when to turn it off.
This is why most four-wheel-drive systems are part-time systems so that they can allow the driver to have the option of switching between a two-wheel and a four-wheel drive.
What are the differences between “Part-time” and “Full-time”?
Part-time four-wheel drive systems are normally operated in two-wheel drive mode for on-road driving but can be switched to two different four-wheel drive modes when driven off-road and in slippery/icy conditions by a flick of a switch or touch of a button.
They also include various settings for multi-geared transfer cases, such as Low-speed four-wheel drive (L4) or high-speed four-wheel drive (H4). The high-speed four-wheel drive position is for conditions that permit the tyres to slip or spin, such as icy or snow-covered roads or off-road. It provides greater drive traction than two-wheel drive. The low-speed four-wheel drive position is for when climbing or descending very steep hills, off-road driving and driving in mud or deep snow.
The low-speed four-wheel drive produces more torque than a high-speed four-wheel drive. However, at the same time, the vehicle drives at a much slower speed when the mode is selected.
It’s important to note that low-speed four-wheel drives do not create more traction. Conversely, it creates more torque at much slower speeds, which means you should NOT travel at high speeds - especially on slippery roads - because things may start to break and your vehicle could potentially break down, making your journey very pricey.
Most part-time four-wheel drive systems have locking and unlocking differentials (Two wheels fixed to the same axle turn at the same speed as a vehicle goes around curves). In order for wheels to turn at different speeds, you have to manually lock a differential. This is helpful for when you come across tricky, off-road situations.
4WD - Pros & Cons
|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|
As for Full time four wheel drive vehicles, they drive extremely well both on-road and off-road. Full time four wheel drive vehicles are always engaged in four-wheel drive high to improve vehicle stability and control. To allow the front wheels to travel at a different speed than the rear wheels, there is an extra centre differential. The full time four wheel drive has impressive traction on hard surfaces but once it is turned off, one wheel can become easily bogged due to the centre differential. When travelling over rough terrain the centre differential can be locked, which allows the vehicle to operate the same as a part-time four-wheel drive in four-wheel drive
All-Wheel Drive (AWD)
All-wheel drive is a more recent technological development to automotive mechanics. Similarly, all-wheel drive is almost the same to a full time four wheel drive - it sends power to all four wheels of the vehicle at all times. However, the primary difference is that all-wheel drive uses a specialised mechanism that’s built into the vehicle and distributes power to the front and the rear - sometimes equally and sometimes biased towards one (or the other depending on what the current road conditions are). It is all automated. Yes, the driver doesn’t have to do a thing, and the traction is substantially improved. Advanced forms of four-wheel drives include torque vectoring, which improves speed and handling in corners for performance vehicles. It is a system used for everyday driving, so it’s good for going over pavement during wet or dry conditions. However, it is not good for going over any rocky or muddy surfaces. That’s more suited to four-wheel drives.
The benefits of all-wheel drive are difficult to ignore compared to a standard four-wheel drive. Some of the best performance vehicles are operated on an all-wheel drive, namely, the Subaru WRX /STI,Volkswagen Golf, Audi RS 8, Porsche 911, and Jaguar F-type, etc. And the fact that it is largely operated by machinery, as mentioned previously, makes it even more appealing. There are sensors on each monitor traction and speed wheels, plus an Engine Control Unit (ECU) that analyzes traction conditions and decides which wheel will receive the most traction.
AWD- Pros and Cons
|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|
Ultimately, it all depends on the drivers’ needs and where you reside. For those who want to drive their vehicle off-road and on rocky terrain, then a four-wheel drive is your best bet. The perfect type of vehicle will most likely be pick-up trucks and SUV. That said, most people tend to think all-wheel drive is the better choice.
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