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All about the all-wheel drive

We are very familiar with the two-wheel drive. The Ambassador and Fiat were two-wheel drive. The engine was in front and a drive shaft transmitted power to the rear wheels. They were rear-wheel drive cars. Since the front wheels turned, they worked well while going around a corner. The rear wheels were fixed so they needed a differential. This allowed the outer wheel to revolve faster then the inner wheel and helped it corner. If both rear wheels, which provided the driving force, turned at the same speed they would have a tendency to push the car in a straight line. Maruti changed everything. It was front engine placed sideways, not longitudinally, and front-wheel drive. To add to the confusion, it was three cylinders. More confusion. The front-engine, front -wheel drive cars did not require a differential. However, since the power was being transmitted to the front wheels, some compensation had to be made. Along came another invention : The constantly variable joint or the CVJ. We are all familiar with the famous World War II jeep and, of course, the Mahindra jeep. These were four-wheel drive jeeps. This means that they were driven by the two rear wheels normally. If you needed more power, you pulled-pushed a couple of levers and through a transfer case attached to the gear box, the two extra wheels, in front would be supplied power. You had all four wheels driving the jeep. There was also a reduction gear that lowered the gear ratio, provided more torque. The car had two-wheel drive in high gear or four-wheel drive in high and four-wheel drive in low gear. In effect, 12-gear ratio with a four-speed gear box.

The Limited Slip Differential or the LSD is another option some manufacturers use. It delivers a better balance of power to either of the drive wheels but retains the turning ability. Now we have all-wheel drive or AWD. Simply put, all four wheels have driving power. It provides greater stability for the car at all times. No debate on this. Some cars have AWD on demand and the driver has the option to engage AWD. This sends power to the second axle only in case of a skid or loss of control of the car. Constant AWD are designed to provide extra road grip and traction at all times. Off-road capability is also enhanced. Some manufacturers who make AWD vehicles have a 60:40 split. 60% power to the rear wheels, 40% to the front wheels. This is perfect for normal driving conditions. If the car hits an icy patch, the front wheels would be destabilised. Automatically, electronically the front wheels would have 60 per cent traction to bring the car under control and 40 per cent power would be to the rear wheels. In rear-wheel drive cars, a skid is one of the most demanding situations. All-wheel drive makes sure a driver does not face such a situation and come with a locking ability. You can maintain the 60-40 per cent drive to the wheels. Gear-reduction capabilities are also available. This, of course, is the ideal combination. It will give your car tremendous stability on road and that extra power if you decide to go off-road.

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