TROUBLESHOOTING TRANSMISSIONS, TRANSFER
CASES, AND DIFFERENTIALS
It does not matter how well your engine is running,
how good the road conditions are, or how proficient an
operator you may be. If the power of the engine of the
vehicle you are operating cannot be transmitted to the
wheels, the vehicle may as well be on the deadline. It is
the function of the transmission to match the vehicle
load requirements to the power and speed of the engine.
The transfer case is used for the same function and, in
addition, allows for the coupling and uncoupling of the
front-wheel drive components. The differential is used
to change the rotational axis of engine torque 90 degrees
from the propeller shaft to the front and rear axles.
Another purpose of the differential is to divide engine
torque between the driving wheels so that they are free
to rotate simultaneously at varying speeds.
This chapter provides information on standard
transmissions, transfer cases, differentials, and the
various indications of abnormal operation so that you
will be able to diagnose the problems with these units
and prescribe corrective action. To obtain more detailed
information on the operation and repair of these units,
refer to the specific manufacturers manuals.
Figure 11-1 shows the location of each of the
components discussed in this chapter.
THE STANDARD TRANSMISSION
The operation of standard transmissions on
automotive vehicles is described in Construction
Mechanic 3 and 2, NAVEDTRA 10644-G1. You should
review chapter 8 of the training course before studying
the material in this section.
Generally, you will not be doing troubleshooting or
repair work yourself. Since you will supervise such
operations, however, it is essential that you know the
proper procedures for performing these duties and for
solving particular maintenance problems.
All transmissions are designed to perform the same
functions. In construction and application, of course,
transmissions vary considerably. One example is shown
Figure 11-1.Location of power train components in a military 5-ton vehicle.