The first car to use an all wheel drive system was the Jensen FF all the way back in 1966. The AWD system is actually synonymous with the regular 4WD, and it means a vehicle with the capability of driving all four wheels at the same time. This can be achieved with the help of a few numerous systems, some of which is more efficient than others. Even though it still isn’t widely used on all cars, this system gives vehicles more grip as well as a nicer set of driving characteristics.
All Wheel Drive (AWD) – A Part-time System
This means the AWD system will actually drive either the front or the rear wheels during regular use. However, the system will use sensors mounted on each wheel to see when one of the wheels will slip. When this happens, the system will send torque to the other axle via either a center differential or via a center clutch. While former is usually used with cars having their engine mounted longitudinally in the front. Those with a transverse front engine will usually use a clutch-based system. This is more compact, but it comes with the inability of enabling AWD manually. This system will only work when it senses a slip, so the car will usually be used as an FWD vehicle.
A Permanent System
One car to use a permanent all wheel drive system is the Impreza. Despite being a sedan, the car boasts a fully permanent AWD system which sends 50% of the power to the front and 50% to the rear. This system, unlike the regular part-time, can be used only with a center differential. This will split the torque evenly and depend on its type it may be able to send as much as 100% of the torque to one particular axle. While this system is usually heavier, it does boast better performance than the clutch-based systems or even than the regular part-time system as it works at all times.
While an all wheel drive system is a great thing to have, it isn’t perfect. While it makes the car have more grip, the system also means the car will become less easy to predict. This is because when it loses its grip, it will do it violently and if the manufacturer doesn’t implement some set of safety systems it may become much harder to drive fast. On top of that, any type of All Wheel Drive system will have e negative effect on the car’s fuel efficiency as there is more weight. It also means there are more things to break and some will avoid it just for that.