4-wheel drive and all-wheel drive are systems implemented by car manufacturers in SUVs and off-road vehicles. Both systems facilitate the transmission of torque from the engine to all four wheels of the car. These systems are helpful for drivers when there is snow, ice or muddy terrain.
4-Wheel Drive Systems
In traditional 2-wheel drive systems, only the front wheels or the rear wheels are powered. If the engine powers the front wheels, they are pulling and turning the rear end wheels. If the torque is transmitted to the rear end wheels, they are pushing the front of the car.
4-wheel drive or ‘four by four’ is a system which allows the transfer of the engine power to all 4 wheels at the same time. This option can be turned on manually by the driver whenever the terrain or weather conditions call for it. The 4-wheel drive option should be turned off on dry pavement. Some cars allow driving on dry roads with the 4x4 system activated, due to an additional set of gears in the transmission case.
4-wheel drive systems have 2 settings: high and low. The low setting is designed for speeds lower than 45 miles per hour. It transmits more torque to the wheels and is recommended when driving off-road, in deep snow or muddy terrain. The ‘4-low’ is not recommended on slippery ground. The high setting is designed for driving on highways at higher speeds.
All-Wheel Drive Systems
All-wheel drive (AWD) systems transmit engine power to all 4 wheels at all times. The power transmission is controlled by the car’s internal system, not by the driver. The car switches to an AWD mode whenever it detects a lack of traction.
The AWD system is also called ‘full-time 4-wheel drive’.
4-Wheel Drive vs All-Wheel Drive
The first important difference between the 2 systems is that the 4-wheel drive system needs to be activated manually by the driver whenever the road conditions require 4 wheel drive. AWD cars to not have an on/off mode switch, so they are best for drivers that do not want to think about traction modes while driving. AWD is a more convenient system.
The 4-wheel drive system has a preset ratio for the torque transmitted to the axles. In AWD, the vehicle’s system can send the amount of power necessary to only one of the axles, considering the wheel with the most traction.
AWD cars are more convenient for urban areas. The 4-wheel drive is a suitable option for off-road due to its ‘low’ mode.
The AWD system is more expensive than the 4-wheel drive. Maintenance costs more and the car needs more fuel. Since all 4 wheels are engaged at all times, the AWD is less fuel efficient.
Both systems are very safe if used properly. Quality tires and appropriate tire pressure are essential. Worn tires can become slippery in AWD systems.
The traction systems are meant to help drivers in difficult road conditions. They do not make a car safer for higher speeds.