Transfer Cases

A part of the four wheel drive system is called a Transfer Case. It is found in four wheel drive vehicles and in all other wheel drive vehicles. Through a drive shaft, a transfer case is joined to the transmission and also to the rear and front axles. It has different names like “transfer box” or “Transfer Gear case” or “Transfer gearbox”.

Functions of Transfer Case
The first function of this is to receive power from the transmission and then transfers this power to the front and rear axles. This function is accomplished with the help of a gear set. Today, most of the manufacturers of Transfer Cases, manufacture such kind of transfer cases which consist chain drive instead of set of gears. The driver controls the features of a set of gears in some vehicles, like four wheel drive (4WD) trucks or in such vehicles which are used for off-road purposes. The mode of the transfer case can be converted according to their applications like whether this is dedicated to a four-wheeler or to a two-wheeler drive (2WD) vehicle. Sometimes, a shifter assists in accomplishing the change of mode of the Transfer case. This is similar to that of a manual transmission. In modern technique, sometimes the method of changing the mode is operated by a switch. In some kind of vehicles, the transfer cases are not selectable and such a transfer case is permanently converted into All Wheel Drive Mode for ever.

Secondly, there may be either one or more than one set of low range gears present in Transfer Case. With a shifter or electronic switch, low range gears are attached. The shifters which are found either in 2WD or 4WD operation, have resemblance with that shifters, which are found in many transfer cases. Low range gears increase the torque at the axles but reduce the speed of the vehicle. During slow speed or high off-road maneuvers, low range gears are used, but in such sports cars based on all-wheel drive, low-range gears are never used. In some very bulky vehicles (military trucks), more than one low-range gears are used.

Types of Transfer Cases
These are mainly divided into five types these are as follows:

Gear Driven Transfer Case
It can utilize gear sets. These are for driving either the front or both for the rear and front drive shafts. These type of cases are used for the heavy units because these are strong enough. These are used in the trucks, but in the recent days, these are also used for the passenger cars.

Chain Driven Transfer Case
More often, to drive the front axle, it use a chain. These cases can also drive the rear axles. In comparison to gear-driven transfer cases, chain driven transfer cases are lighter and smoother. The vehicles in which these chain driven transfer cases are used are: full size trucks, compact trucks, jeeps and SUVs. Although chain transfer cases are lighter and calmer than the gear driven transfer cases, but as far as power is concerned, these are weaker in capacity.

Independent Transfer Case
The transmission part is completely isolated from the Independent Transfer Case. To adjust this type of configuration, a small size drive shaft is sent to the independent transfer case form the transmission.

Married Transfer Case
Married transfer cases are directly bolted to the transmission. In some cases, married transfer cases are become the inbuilt part of transmission. In such case, both these two components share the same housing. Married transfer cases are the most common type of transfer case. These transfer cases are used in pickups. Cars and SUVs.

Manual Transfer Case
There is a selector lever on the driver side floor transmission hump of a Manual Transfer case. This is available in two options—one in either two manual front axle hub selectors of “Free” or “LOCK” and “UNLOCK” or two sealed automatic locking front axle hubs. The vehicle must be either at a complete stop or it must be slowly rolling to engage or disengage.

Electronic Shift on the fly (ESOF) Transfer Case
ESOF Transfer Cases have buttons with front sealed automatic locking axle hubs or a dash mounted selector switch. In such transfer case system, unlike the manual transfer case, there is a transfer case motor and vacuum operated front hubs. By engaging the transfer case, the speed up to 55 mph can be derived and disengaging it, the vehicle can be stopped completely.