Four Wheel Drive Systems

The demand for four-wheel-drive vehicles as a lifestyle vehicle in Malaysia is increasing every year. Once, people used to associate pick-up vehicle with "construction site" or Thailand. Nowadays, there are a lot of trendy pick-ups running on our road. An example is the Ford Ranger. But, how many of us really know what is a four-wheel-drive system?

There are a few types of four-wheel-drive systems available in the market. They are automatic four-wheel drive system, part-time four-wheel drive system, full time four-wheel drive system and all wheel-drive system.

In automatic four-wheel drive system, when in normal mode, the vehicle travels in two-wheel drive and typically with rear wheels being the driven wheels. A driver can set an "auto 4WD' function with a touch of a button on the dashboard. The vehicle will then decide when to activate and de-activate four-wheel drive.

When the vehicle engages four-wheel drive, it manages to transmit the power; as necessary, to both front and rear wheels or to wheels with the most traction. The driver can also switch to low gear for improve torque in off-road terrain.

An automatic four-wheel drive system requires a centre differential or some kind of viscous coupling or multi-plate clutch, a transfer case, two drives hafts, two axle differentials and two powered axles. An example of an automatic four-wheel drive vehicle is the Jeep Grand Cherokee.

Meanwhile, the most basic four-wheel drive system is the part-time four-wheel drive system that is available in many four-wheel drive vehicles. In normal mode, the vehicle travels in two wheel-drive, typically with rear wheels receiving power and pushing along the front. The driver is responsible for engaging and disengaging the four-wheel drive. By activating the four-wheel drive, the power is sent to the front wheels and continues to power the rear as well.

When on off-road terrain, the driver can engage an extra-low gear for improved torque while in four-wheel drive mode. A part-time four-wheel drive system requires a transfer case, two drives hafts, two axle differentials and two powered axle and does not include a centre differential. An example of this vehicle is the Ford Ranger.

A full-time or permanent four wheel drive system has no two- wheel-drive mode. They always operate with power going to all four wheels, so the drive can benefit all the time from four-wheel traction. There is also no way to turn off the four-wheel drive. A full- time four-wheel drive requires a centre differential, transfer case, two driveshafts, two axle differentials and two powered axles. In rough off-road terrain, the drive can engage low range for improved torque. An example of a full-time four-wheel drive vehicle is the Perodua Kembara.

Meanwhile, an all-wheel drive system is used mostly in cars. An example of an all-wheel drive car is Subaru Impreza.