The transfer case switches between high-speed four-wheel drive (4H) and low-speed four-wheel drive (4L) modes through different gear ratios. 4L mode amplifies torque by increasing the gear ratio, typically by 2-4 times, for extreme off-road extrication. 4H mode distributes power through the transfer case's smaller gear ratio, balancing power output and vehicle speed; 4L mode further amplifies torque by increasing the gear ratio, with some models achieving a torque amplification of 2-4 times.
Full-time four-wheel drive and some part-time four-wheel drive transfer cases integrate a central differential, allowing for a speed difference between the front and rear axles. The central differential lock locks the differential when needed, achieving a rigid connection between the front and rear axles to enhance extrication capabilities. When locked, the power distribution between the front and rear axles is 50:50. Differential locks include mechanical (such as gear engagement, Torsen differentials) and electronically controlled (such as multi-plate clutches).
