4WD vs AWD

Often I get asked what is the difference between a four-wheel drive (4wd) and an all-wheel drive (AWD)? The simple answer is a 4wd is designed for off-road use while an AWD provides better stability and traction on the bitumen. 

There is however a variety of reasons why a 4wd is different from an AWD. Before we explore what some of these differences are it is important to mention that are many examples of full-time 4wd systems (such as the 200 series Land Cruiser and the Land Rover Discovery). This is a combination of both the 4wd and AWD system as they utilise the benefits of an AWD when driving on  sealed roads, but also have the ability to drive into low traction areas.

Let's start with the Four Wheel Drive system

Part time 4wd system
(Credit Dykes, 2013)

For usual driving conditions, majority of 4wds will be a rear-wheel driven until 4wd is engaged. This is known as a part-time 4wd system as the name suggests, the vehicle is only in 4wd part of the time. The driver will leave the vehicle in 2H which stands for two-wheel drive high range when travelling along in normal road conditions. As a general rule, part-time four-wheel drives will have a separate gear selector that allows for the driver to choose whether they are in 2H, 4H or 4L (there are some 4wds such as the Volkswagon Amarok that doesn't have 4L, but utilises an off-road mode instead). 

Let's start with the main key difference between 4wd and an AWD, which is the ability to go into Low Range (4L) on surfaces that have minimal traction. Areas such as steep rock climbs and soft sand are just some of the common areas where low range is best. The low range system changes the gear ratio in order to provide additional torque to the axles, which allows climbing over obstacles a million times easier. 

The 4wd system utilises the transfer case to distribute power to each differential 50:50. The power is then distributed by the front and rear diff to each axle, allowing for the vehicle to navigate around obsticles. The issue with this system is that each diff will send power to the axle with the least resistance. In practical terms, when one wheel is lifted off, power will be sent to the one in the air rather then the wheel that is on the ground. This can also be seen in low traction surfaces, as the tyre that cannot grip onto the track will continually spin, while the wheel that is needed to continue pushing the vehicle fowards doesn't move. This downside of many 4wd systems with an open diff can be imporved with a limited slip differential (LSD) or fixed by fitting a locker.

As mentioned, the 4wd system is designed to explore off the beaten track in low traction areas. This differs significantly from the design of the AWD system. 

So what is an All Wheel Drive?

All Wheel Drive System

The AWD system is built and utilised to provide additional safety for drivers when travelling along the bitumen. This system relies upon the computer to manage the drive train and make adaptations when necessary. The AWD system will distribute power evenly across all 4 wheels to reduce wheel spin and any loss of traction through a centre diff. The centre diff splits the power and torque away from the tyre that is spinning too much, which allows for the system to prevent wheel spin, particularly in wet conditions.  

The centre diff works with the computer system to send power to the tyre that needs it the most. This allows for the wheels to easily grip on to the road and maintain traction. It is through this ability that AWDs tend to be the safest system on the road, as wheel spin and lost of traction rarely occurs.

What should I purchase?

Well to answer this question, it really depends on what you intend to use your vehicle for. If you don't head off road and would like to have additional safety features then an AWD is what you should pick. However these vehicles are still not 4wds, therefore they don't belong on the tracks (there are many people who will disagree) as these vehicles are not designed for what we put our 4wds through.

For me, I would pick a 4wd. Hence why this is a 4wd and camping blog. The ability to explore parts of our country that the general population will never see is amazing and that's why I love this hobby. 

The best of both worlds is in full time 4wds which work as an AWD on the road, then have the ability to undergo hard core offroading as well. However these vehicles usually tend to be heavier on fuel but that is a compormise for the additional safety features. 

Now there are definetly pros and cons to each system, however this is the difference between each system in simple terms. 

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The Part time 4wd system diagram used in this post were not created by me. This image can be found at-  Alphabet Soup: 4×4 vs 4WD vs AWD Where’s the Differential?