A transfer case is one of the serviceable components in a four wheel drive system. Present in both full-time and part-time 4WD vehicles, the transfer case operates with the help of gears and, in many modern cars, a chain. Usually, a transfer case indirectly connects to the transmission’s rear. The transmission sends power to the transfer case which in turn sends the power, or torque, to the front and rear drive shafts. Because of the transfer case, the wheels can spin at the same speed, and the vehicle is able to enter or maintain its four wheel drive. Often, part-time 4WD vehicles use a transfer case with an extra set of gears that allows for the creation of extra torque through the selection of a high or low gear range. This can make it easier to climb steep hills and mountains. Transfer cases also contain a lubricant that keeps gears running correctly. Because they are a significant part of the 4WD system, it is important that drivers maintain them.