The difference between a 4 low and 4 high 4WD system is primarily in the gearing and the power transfer they provide to a vehicle.
4 low is a low-range gear that uses a low gear ratio to provide extra torque and pulling power for off-road activities such as rock crawling and hill climbing. When in 4 low, the power transfer to the wheels is more direct than in 4 high, allowing the vehicle to move forward with greater force. This is beneficial for maneuvering over difficult terrain and can also be used to help get the vehicle unstuck from mud or sand.
4 high, on the other hand, is a high-range gear that uses a higher gear ratio to provide less power transfer to the wheels for higher top speeds. This is beneficial for on-road use, as it helps the vehicle to accelerate faster and reach its maximum speed more quickly.
Overall, 4 low and 4 high provide distinct advantages for different purposes. 4 low is ideal for off-roading activities due to its increased torque and pulling power, while 4 high is better suited for on-road driving due to its higher top speed. It is important to note that 4 low and 4 high can only be used in 4WD systems and cannot be used in 2WD systems.