A mechanical component found in four-wheel drive (4WD) and all-wheel drive (AWD) vehicles, it’s a gearbox that distributes power from the transmission to both the front and rear axles. Functionally, it accepts power from the transmission and splits it, sending it to both drive shafts. In a part-time 4WD system, it typically allows the driver to select between two-wheel drive (2WD), four-wheel high (4H), and four-wheel low (4L) ranges. An example of its use is enabling a pickup truck to shift into 4L for increased torque when traversing difficult terrain.
This vital mechanism allows for enhanced traction in challenging conditions such as snow, mud, or rocky surfaces. The capability to shift into different drive modes provides versatility, optimizing fuel efficiency on paved roads in 2WD while providing necessary grip when off-road in 4WD. Historically, these systems were manually operated, requiring the driver to engage the mechanism. Modern systems often feature electronic controls and automatic engagement, increasing user convenience. Their implementation can significantly extend the usable range of a vehicle and improve its overall capability.