What do L4 and H4 mean in four-wheel drive?

[BeauDella]

H4 stands for High-speed four-wheel drive, while L4 stands for Low-speed four-wheel drive. Here are the relevant introductions: 1. Application of high and low-speed four-wheel drive: High-speed four-wheel drive is suitable for driving on gravel roads, muddy roads, snow, and sandy areas, with the maximum speed generally controlled within 80KM. Low-speed four-wheel drive provides high torque, meaning it's more powerful, suitable for off-roading, climbing, descending steep slopes, and getting out of tough situations, but rarely used for continuous driving. When using 4L, it's best to start in 1st gear and avoid shifting to gears above 2nd, while keeping the speed not too high. Use L4 when driving slowly and H4 when driving fast. Use automatic mode when not off-roading. 2. Introduction to four-wheel drive: Four-wheel drive refers to a vehicle maintaining four-wheel drive throughout the entire driving process, with the engine's torque distributed to the front and rear wheels at a fixed ratio. This drive mode ensures good off-road and handling performance at all times, but cannot adjust torque distribution based on road conditions and has higher fuel consumption. On the other hand, real-time four-wheel drive is controlled by a computer chip to switch between two-wheel and four-wheel drive. On normal roads, the vehicle drives in two-wheel drive mode. When encountering off-road conditions or wheel slippage, the computer detects and automatically distributes power to the other two wheels. For part-time four-wheel drive mode, the quality of the control program affects the intelligence of the drive mode switching. Additionally, there is also a part-time four-wheel drive (Part-Time 4WD) that is manually controlled by the driver to switch drive modes. Many SUVs and off-road vehicles have one or several of the above four-wheel drive modes to complement each other's strengths and weaknesses.

[ONatalie]

When I first studied 4WD systems, I also couldn't understand what these letters meant. Simply put, L4 stands for low-range four-wheel drive, which is essential for extreme conditions like climbing steep slopes or navigating through mud pits. This mode locks the center differential, creating a rigid connection between all four wheels, while also amplifying torque through the transfer case, allowing the vehicle to cling to the ground like a gecko. However, you shouldn't use it on regular roads—it can cause the driveshaft to make cracking noises during turns and significantly increases fuel consumption. For example, our worksite pickup truck in mountainous areas immediately switches to L4 when encountering landslide sections—it's more reliable than any electronic system.

[LydiaRose]

Last time I drove my friend's off-road vehicle, I finally understood that H4 actually stands for high-speed four-wheel drive. I often use this mode when driving on national highways in rain or snow, as having power on all four wheels makes it less prone to skidding. The biggest difference from L4 is that it can switch modes while driving, and can still be used at speeds of 70-80 km/h. However, I've noticed that prolonged use of H4 on paved roads can cause abnormal tire wear and make the steering feel heavy. Nowadays, the principle of on-demand four-wheel drive in urban SUVs is quite similar, but off-road veterans always say that mechanical H4 is more reliable for getting out of tough situations.

[JesseFitz]

The L4 gear on the transfer case is a lifesaver. When engaged, the engine torque instantly doubles or even triples, and even with the tachometer hitting 4,000 RPM, the vehicle moves at a walking pace. Last year, when I got stuck on the beach, switching to L4 along with the differential lock allowed the tires to dig through the sand and pull me out. However, this mode has many limitations: you must stop and shift to neutral to engage it, the steering makes loud cracking noises when turned to full lock, and using it on asphalt roads can damage the driveshaft in minutes.

[McLuke]

Beginners often confuse these two modes. Simply put, H4 is like an everyday umbrella for slippery roads, while L4 is more like a rescue rope, specifically designed for shell craters and steep slopes over 35 degrees. Once, while driving with my family on an icy mountain road, switching to H4 helped us safely cross the pass. But remember, you must come to a complete stop before shifting to L4, or the transmission might give you trouble. Nowadays, many vehicles have simplified this to knob operation, making physical gear levers quite rare.