that it will drive the rear wheels at all times and drive
the front wheels when needed.
The transfer case can be mounted in several ways
in a vehicle. It can be a separate component mounted to
the rear of the transmission and driven by a propeller
shaft connecting it to the output of the transmission. It
can also be a part of the transmission (fig. 11-10) and
driven by a gear or by the output shaft of the
transmission. The transfer case performs one or more of
the following functions:
It transfers the transmission power to a point low
enough so that a propeller shaft can be mounted
under the engine and power the front axle.
It provides an output to power one or more rear
It provides a high and low gear ratio for vehicles
that do not have the necessary gear reductions in
It provides arrangements for engaging and
disengaging front-wheel drive and high and low
ranges when applicable.
One of the mechanics jobs is to repair transfer
cases; this means diagnosing trouble, dismantling,
inspecting, and reassembling the unit. If you become
familiar with the method of repairing one particular
transfer case, you should not have much difficulty
The first indication of trouble within a transfer case,
as with other components of the power train, is usually
noisy operation. If an operator reports trouble, make
a visual inspection before removing the unit from the
vehicle. Check for such things as oil level, oil leakage,
and water in the oil.
Make sure the shift lever linkages are inspected. If
the shift lever linkages are bent or improperly
lubricated, it will be hard to shift the transfer case or, in
some cases, will make shifting impossible. Make sure
other possible troubles, such as clutch slippage,
damaged propeller shaft, and damaged axles, have been
Worn or broken gears, worn bearings, and excessive
end play in the shafts will cause noisy operation of the
transfer case. When it is determined that the trouble is
within the transfer case, have your personnel remove the
unit from the vehicle for repairs.
Make sure the transfer case is thoroughly cleaned
before disassembly of the unit begins. When the unit is
disassembled, have each part cleaned with an approved
cleaning solvent. Inspection of the individual parts
should follow the same procedure as outlined for
transmissions. Avoid waste by using old parts that are in
good condition. Table 11-2 is a troubleshooting chart for
transfer cases. As referenced in the chart, you should
refer to figures 11-11, 11-12, 11-13, and 11-14
Personnel who are not thoroughly familiar with a
particular make and model of a transfer case should be
supplied with a manufacturers repair manual. Check
the job frequently to be sure the proper adjustments and
assembly procedures are followed.
Figure 11-10.Transfer case to the transmission.