Four Wheel Drive

The first mass produced four wheel drive system, abbreviated 4WD, was first made in 1903 by Mercedes. Four wheel drive went on to be a way of life for many people, creating a significant market for off-road vehicles in much of northern and rural America . Just as rear wheel drive vehicles are often designed to be fast, four wheel drive vehicles are often designed or customized to be big. Through lift kits and large tires, custom truck owners seem to have their own image among America 's drivers.

Typical four wheel drive systems are really only part time, in that the driver may turn the option on or off for slippery or off-road applications, as having the system on all the time takes more power to run hence reducing gas mileage and engine life. Most of the time these four wheel drive systems simply run as rear wheel drive vehicles. In the case of domestic trucks, the rear wheel drive parts are often interchangable with those from cars. Also, four wheel drive systems are usually not truly four wheel drive. Since the rotational velocity is greater for the outer wheel than it is for the inner when a vehicle is turning, most of today's trucks and SUVs only have power to one wheel in the front and one wheel in the rear to prevent tire wear when cornering. This is not true for all vehicles, though, as there were a few trucks made throughout the 1970's and 1980's that came with true four wheel drive systems, in that all four wheels had power when the system was turned on. Some of these systems were even on all the time.

Due to their weights, four wheel drive systems are usually reserved for larger vehicles or in vehicles where weight does not matter. What makes the systems particularly heavy is the fact that both the differentials for the front and rear drive systems are required to make it work. A notable amount of weight is also present in the device that splits the engines power between the front and rear wheels, known as the transfer case. This added mechanism also takes more room under the vehicle, essentially eliminating compact cars from the ability to run four wheel drive. There were a few four wheel drive cars on the marked in the 1980's, such as the Subaru 1600 series, but they were either discontinued or moved to all wheel drive by the 1990's, due to the extra weight, difficulty of maintenance, and cost of production.

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Russell Gillmore 2004 F03