How Does a 4x4 Transfer Case Work?

The transfer case is part of the four-wheel-drive system in vehicles such as this Jeep.

The transfer case is part of the drive line of four-wheel-drive vehicles. Located behind the transmission, the transfer case sends power to the front and real axles by way of front and rear drive shafts. Most transfer cases also allow two-wheel-drive operation.

Main Shaft

The main shaft of a transfer case receives torque (rotational power) from the transmission output shaft. At the rear of the transfer case, the main shaft output connects to the rear drive shaft to power the rear wheels.

Low-Range Gear

The low-range gear system is associated with the main input shaft. This system often uses a planetary gear set, and allows the driver to select a low gear option for additional engine power at low vehicle speeds. In most cases, low range is only available when four-wheel-drive is engaged.

Four-Wheel-Drive

The main shaft power is transferred to the front output shaft either by a gear set or, more commonly, a chain and sprocket drive system. When the user selects four-wheel-drive, the front output gear or sprocket system engages the main shaft, thus rotating the front output shaft. A drive shaft connects the transfer case front output shaft to the front axle.

References

• "Jeep Cherokee 1984 thru 2001"; Henderson, B., and Haynes, J.; 2005

Resources

• Read this Article in Spanish