The Age Old Confusion between All Wheel Drive & Four Wheel Drive Vehicles

As we know, today’s SUV market is divided into three categories. Namely, Two Wheel Drive Vehicles, All Wheel Drive Vehicles and Four Wheel Drive Vehicles.

Two Wheel Drive vehicles are those where the power from the engine is sent to either the rear axle or the front axle, resulting in power to only the rear two tyres or the front two tyres. These vehicles are good for the normal city commute that you may do, to and from work. These vehicles have very limited capabilities when it comes to off-road work and find themselves completely out of place in such scenarios. The major reason behind this is the lack of power to all four tyres of the vehicle. This means that at any given time, the vehicle will be dragging along, at least two of its tyres. The power is split between the front two or rear two tyres with the use of an open differential. This enables different tyres on the drive train to turn at different speeds making it possible to turn the vehicle without breaking or damaging any components.

 

Going one step forward from Two Wheel Drive Vehicles, is the introduction of All Wheel Drive Vehicles. In these vehicles, under normal circumstances, the power from the engine is sent to all four tyres with the help of an open central differential. These are good for the weekend camper who likes to drive on unsealed roads to reach various campsites. The traction available with these drivetrains outperforms that from two wheel drives, monumentally! The key to the added traction is the power transfer to all four tyres. These vehicles are particularly good for driving over unsealed and corrugated tracks. Given, the added advantage of all wheel drive set ups over the two wheel drive vehicles, it is important to understand that hard and technical bush driving is not their forte. The problem arises when one tyre is lifted off the ground. When this happens, all the power from the engine goes straight to the tyre with the least traction and you end up going nowhere with one tyre spinning out of control in mid-air

 

To overcome this issue, four wheel drive vehicles are designed, keeping in mind added traction, while off the beaten path. Most of these four wheel drive vehicles are set up as either two wheel drives or all-wheel drive vehicles while on the road, with an option of a locking central differential while doing bush work. Locking this central differential ensures a perfect 50:50 power split between the front and rear axles. This means that no matter what, there will be equal power going into the front and rear axles. It is important to note that locking the open differential does not mean 100% traction for the vehicle. The power received by each axle is then divided between the two tyres, again through an open front or open rear differential. This means that the tyre with the least traction on the said axle, will end up with all the power. A lot of times, this results in your vehicle effectively sending power to only 2 tyres at a time.

This set up is generally more than capable of getting you across most of the obstacles that you may encounter. In today’s electronically advanced world, most vehicles come equipped with added traction control systems that attempt to ‘fool’ the differential into thinking all the tyres have the same amount of traction to ensure that the power is equally being split amongst the tyres.

There are various other traction aids that can be added to your four wheel drive, like front and rear differential locks, which would enormously increase its off-road capabilities. Stay tuned to know more about these extra traction aids and what to do when these aids fail on you and you get stuck – it happens to everyone!  

- Sujay Vasist, - All Four x 4 Spares Researcher & Content Writer