Chapter 26. AUXILIARY TRANSMISSIONS, SUBTRANSMISSIONS, AND OVERDRIVES

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Figure 25-15. Final Drive Assembly

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TM-9-8000 Principles of Automotive Vehicles Manual

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Figure 26-2. Auxiliary Transmission - Sectional View.

TM 9-8000

CHAPTER 26

AUXILIARY TRANSMISSIONS, SUBTRANSMISSIONS, AND OVERDRIVES

Section I. AUXILIARY TRANSMISSIONS

them because a low-speed range is available for pulling

26-1. Purpose. An auxiliary transmission (fig. 26-1) is

power and a high-speed (direct-drive) range is available

used to compound the number of gear ratios that are

for highway usage.

available from the main transmission. It usually is a

separate two-speed transmission that mounts in series

26-2. Operation (Fig. 26-2). The auxiliary transmission

between the transmission and the driving axle by utilizing

two propeller shafts. By providing two speeds, the

is controlled by a lever in the driver's compartment. The

auxiliary transmission effectively will double the number

gear ratios usually are selected in the box by a sliding

of gear ratios available from the main transmission.

dog clutch. The gear ratios of the auxiliary transmission

Vehicles equipped with auxiliary transmissions generally

must be selected while the vehicle is not in motion.

are more versatile than vehicles without

Figure 26-1. Typical Location of Auxiliary Transmission.

TA233755

26-1