4A is a driving mode that automatically adjusts the vehicle's power distribution when road conditions change, allowing for smoother driving. On-demand four-wheel drive: As the name suggests, on-demand four-wheel drive is a system that engages only when necessary. Vehicles equipped with this system typically operate in two-wheel drive on urban roads. The system only activates when the onboard computer detects wheel slip or loss of traction, switching between four-wheel and two-wheel drive by connecting or disconnecting the transfer case. The advantage is its economic and convenient operation without manual intervention, though its off-road capability is weaker compared to other four-wheel drive modes. It usually takes at least one second for the differential to lock. Part-time four-wheel drive: Normally operating in two-wheel drive, engaging the transfer case creates a rigid connection between the front and rear axles, distributing power equally to all four wheels. Some high-end off-road vehicles often feature front, center, and rear differential locks, typically with 4L and 4H modes. Since locking the front and rear drives eliminates speed differences between wheels, theoretically, on high-traction paved roads, 4H and 4L modes cannot be used at high speeds due to steering interference, which could damage the differential or cause rollover accidents. Part-time four-wheel drive does not improve high-speed stability or body tracking on slippery surfaces.
