CHAPTER 11 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 manufacturer's 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.