What is On-Demand Four-Wheel Drive?
2 Answers
On-demand four-wheel drive is a system where the computer automatically detects and immediately distributes the engine's output torque to the two front wheels when encountering poor road conditions or wheel slippage, naturally switching to four-wheel drive mode, making it simpler to use. On-demand four-wheel drive means the system automatically activates four-wheel drive only when the vehicle encounters conditions that require it, otherwise operating in two-wheel drive mode. Each driven wheel of a car must have a differential to enable turning on high-traction surfaces, as different wheels rotate at different speeds during a turn. The differential is the component that eliminates this speed difference, and full-time four-wheel drive was developed based on this concept.
When chatting while driving, people often ask me what exactly an all-wheel drive (AWD) system is. Actually, this system is quite common in regular SUVs. It uses front-wheel drive during normal driving to save fuel, but once the front wheels slip—such as on rainy or snowy roads—the system automatically detects it via sensors and switches to four-wheel drive mode, providing instant traction. The entire process is controlled by the onboard computer without requiring manual operation. This design is both safe and economical because it only activates when needed, unlike full-time four-wheel drive, which constantly consumes fuel. I find it especially practical for city driving, as it prevents slipping on wet roads, though it’s not as powerful as full-time four-wheel drive for off-roading. Regular maintenance is crucial to ensure the sensors stay clean and avoid misjudgments.
