At one time, the only vehicles to have Four Wheel Drive (also known as 4WD or 4X4) were ‘off-road’ vehicles such as Jeeps and military vehicles. Nowadays, there are also a number of ‘on-road’ hi-performance cars fitted with 4WD. These have 4WD for stability and traction on the road, especially when driving in poor conditions and for increased acceleration.

Audi was the first maker to use 4x4 successfully in a performance production car. This was back in 1982 when they introduced the Audi Coupe Turbo Quattro. This car has been an influence since.

When do you need Four Wheel Drive?

All two wheel drive cars are either Front Wheel Drive (FWD) or Rear Wheel Drive (RWD). These are known as 4X2. There are four wheels on the car but there are only ever two wheels that propel the car along.

If too much power is applied to these driving wheels or the road surface is slippery then the tyres are likely to lose traction (loss of grip) resulting in ‘wheel spin’.

Imagine the situation, it is raining slightly and you decide to accelerate quickly from a junction. The car does not move from the spot, instead the wheels start spinning furiously, making a terrible noise, going nowhere and attracting the attention of passing pedestrians much to your embarrassment. Four Wheel Drive comes into effect in such a situation to deliver drive to the other pair of wheels at the same time and generate enough grip to safely pull away. The same situation occurs in extreme surface conditions such as snow or mud, when the only way to get going again may be by being towed out by a Four Wheel Drive vehicle.

When does the Four Wheel Drive work?

All four wheels can be driven all of the time (permanent or full-time) or just some of the time (part-time), depending on when the system is active (e.g. engaged automatically when the wheels have no traction or when selected manually). If the 4WD option is automatically controlled then it will just work by itself. If you have to engage it manually then you select it by shifting a lever to a certain position. There are usually two positions for 4WD: ‘High 4’ and ‘Low 4’. ‘High 4’ would be used for dusty dirt roads or on rain drenched roads and ‘Low 4’ would be used for driving on sand, snow or deep mud surfaces at much lower speeds.

 
The typical Four Wheel Drive system comprises of a Gearbox in manual or automatic form, a transfer box that selects and divides the power to either 2 or 4 wheel drive and two sets of driving axles or drive shafts.

With modern day systems the Four Wheel Drive becomes active when the wheels start to spin. This is all sensed electronically and the system takes over by applying more power to the wheels that are not spinning. When the wheels have stopped spinning the system then reverts back to supplying power to just one pair of wheels. This all happens very quickly and smoothly making the car safer and more pleasant to drive in all conditions.

The downside to having a Four Wheel Drive car is that they are slightly more thirsty on fuel and a little more to service.