What does 4x4 mean in cars?
2 Answers
4x4 on a car indicates that the vehicle has 4 wheels, with 4 of them being drive wheels. 4x4 can be understood as a four-wheel drive vehicle equipped with a four-wheel drive system. The number before the 'x' represents the total number of wheels on the car, while the number after the 'x' indicates the number of drive wheels. Four-wheel drive is mainly divided into three categories: On-demand 4WD: On normal road surfaces, the vehicle typically operates in rear-wheel drive mode. Once poor road conditions or wheel slippage is detected, the computer automatically adjusts and immediately distributes the engine's torque to the two front wheels, naturally switching to four-wheel drive mode. Its biggest advantage is ease of operation, but due to computer control, the vehicle's response may be slightly slower. Part-time 4WD: The driver can manually switch between two-wheel drive and four-wheel drive modes by engaging or disengaging the transfer case based on road conditions, allowing for free conversion between 2WD and 4WD. This is suitable for RVs and urban sports cars. Full-time 4WD: This drivetrain maintains a permanent four-wheel drive mode, with the engine's torque evenly distributed between the front and rear wheels during driving, ensuring equal torque to both sets of wheels. Full-time 4WD systems offer excellent driving control and tracking performance. However, this system consumes more fuel and has poor fuel economy. Full-time 4WD is suitable for professional off-road vehicles. The four-wheel drive system in sedans is a constant-mesh type, incorporating a viscous coupling that eliminates the need for a manual transfer case, automatically distributing torque between the front and rear tires as needed. On paved roads, a 4WD vehicle distributes 92% of the engine's torque to the front wheels and 8% to the rear wheels. However, on unpaved roads, at least 40% of the engine's torque is allocated to the rear wheels. When the front wheels start to slip, the speed difference between the front and rear wheels causes the fluid in the coupling to thicken immediately and lock the coupling, directing the engine's torque solely to the rear wheels. Once the front and rear wheel speeds equalize, the original drive mode is automatically restored.
My off-road vehicle is a 4×4, which simply means all four wheels can receive power. Regular two-wheel-drive vehicles can only power either the front or rear wheels, whereas this all-wheel-drive design provides better traction on muddy terrain, snowy slopes, or gravel roads, making it less prone to slipping. Last time I went camping in the mountains and encountered a steep slope, the two-wheel-drive cars in our group couldn’t make it up, but my vehicle climbed it effortlessly. However, it’s worth noting that these vehicles consume more fuel, making them somewhat wasteful for daily city commuting—they’re better suited for outdoor enthusiasts. Additionally, some modern urban SUVs use a smarter on-demand four-wheel-drive system that operates in fuel-saving two-wheel-drive mode by default and only activates four-wheel-drive automatically when wheel slippage is detected.
