A transfer case assembly is a mechanical device in a four-wheel drive (4WD) vehicle that splits the engine's power between the front and rear axles. It allows for different driving modes, such as two-wheel drive, four-wheel drive, and low-range four-wheel drive.

The primary function of a transfer case is to distribute power from the transmission to the front and rear axles. It also contains gears that allow for different gear ratios, providing additional torque for off-road driving or towing heavy loads.