All four-wheel drive vehicles come with a transfer case. The box, located just behind the transmission, takes the torque generated by the engine and distributes it to the driveshafts. This part also synchronizes wheel rotations and can contain low range gears so you can take the vehicle off road. There are several options used by four wheel drive vehicles.

Unit Types

There are two main options in unit types. Each one has its benefits depending on the use of the vehicle. One type is the gear-driven transfer case. This system uses gear sets to drive the front and rear driveshafts. This layout works well with strong and heavy units. They are commonly on larger trucks. However, they appear more frequently in passenger cars.

Chain driven designs only drive a single shaft. On rare occasions, some vehicles use this design to drive both axles. These are quieter than a gear driven version. Compact trucks, jeeps, SUVs, and large trucks use this type of driving. However, many serious off-road drivers change this type of design to a gear-driven model. They prefer the extra strength provided by the drive and put up with the extra noise.

Transfer Case Shift Types

As with transmission types, there are a few different gear types. One is electronic shift on the fly (ESOF). This type of change comes with a dash-mounted selector that selects between all-wheel drive and two-wheel drive. To activate the four-wheel drive high selector, you must drive at a lower gear. If you want to engage four-wheel drive low, you must stop the vehicle and put the transmission in neutral.

The other type of actuation is manual shift on the fly (MSOF). The MSOF has a selector lever located on the floor drive hump. This type of derailleur sometimes has two sealed automatic front axle hubs with lock, unlock, or free selectors. As with ESOF, to activate the high setting, your vehicle must be moving at a low speed. The vehicle, to shift into low speed transmission, must be in neutral with the vehicle stopped.

accommodation

When it comes to housing, like everything else, there are a couple of different options. The first option is a married housing transfer case. This means that the part is bolted directly to the transmission. With this housing, it sits between the transmission output shaft and the rear of the main driveshaft. In some cases, the case is part of the transmission and the two share the same dwelling.

The other type of housing is a divorced/independent model. Unlike the married version, this one does not mount directly to the transmission. Instead, it is located away from the transmission and connected by a driveshaft. This type of housing is found only on vehicles with a long wheelbase, such as a military or commercial vehicle.

A transfer case can be a combination of any of these types. A chain-driven model may be MSOF and contained in a married housing, for example. The design of the piece will depend on the manufacturer.