What are the 4HLc and 4LLc central differential systems?
2 Answers
4HLc is a high-speed four-wheel drive system with a central differential, while 4LLc is a low-speed four-wheel drive system with a central differential. Here is relevant information about the central differential system: 1. When a four-wheel-drive vehicle is in part-time four-wheel-drive mode with the central differential locked, driving on dry roads tends to make the vehicle go straight. This is because both left and right wheels have high traction, causing a speed difference between them during turns due to their different travel distances. The speed difference is transmitted to the front and rear drive shafts via the differentials on the axles. Without a central differential to resolve this speed difference, the resulting force will restrict the wheels from rotating freely with the ground, leading to steering difficulties. If the speed is too high, this may even cause the vehicle to overturn. 2. If the differentials on the front and rear axles are further locked in part-time four-wheel-drive mode, it becomes nearly impossible for the vehicle to turn on paved roads. Sudden locking of the axle differentials during normal driving can easily cause the vehicle to overturn. 3. After locking the central differential and the axle differentials, the engine's power may concentrate on the wheels that still have traction while the others slip. However, the vehicle's drivetrain is designed to distribute the engine's torque equally among all four wheels. If only one or two wheels have traction, the torque they receive may exceed the drivetrain's capacity.
4hlc and 4llc are common central differential system modes for four-wheel-drive vehicles. Simply put, 4hlc stands for 4 High Lock Center, which means high-speed four-wheel drive with the central differential locked. I often use it on highways or slippery roads during road trips to prevent wheel slippage and enhance stability, making it suitable for daily driving to avoid loss of control. 4llc, on the other hand, stands for 4 Low Lock Center, which is low-speed four-wheel drive with the central differential locked. I use it when off-roading or climbing steep slopes to increase torque output and provide greater traction for tackling muddy or gravel terrain. The key to distinguishing them lies in their application scenarios: avoid using 4llc at high speeds to prevent damaging the transmission, and don’t miss out on the advantages of 4llc at low speeds. Regularly check the drivetrain to ensure smooth mode switching—safety first, and avoid prolonged differential locking to prevent component wear. Choosing the right mode makes driving more worry-free and efficient while protecting the vehicle and extending its lifespan.
