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TM 9-8000
a. Neutral. The gears are shown in the neutral position
first to second speed, both sliding gears have been
shifted rearward; the first-and-reverse speed main
in figure 22-2. The input shaft drives the countershaft
shaft gear has been shifted out of engagement into the
through the main drive gear and countershaft drive gear.
neutral position and the second-and-third speed main
None of the countershaft gears are in mesh with the
shaft gear has been shifted into mesh with the
main shaft sliding gears, however, so the main shaft is
countershaft second-speed gear. The input shaft,
not driven. When the gears are in this position, there is
through its integral main drive gear, is now driving the
no connection between the engine and the driving
countershaft through the countershaft drive gear (as is
wheels, so the vehicle remains stationary while the
the case in all speeds), and the counter-shaft is driving
engine is running. The path of transmitted power is
the main shaft through the countershaft second-speed
shown by the arrows.
b. Low Speed. When the gears are in first-speed
gear and the second-and-third speed main shaft gear as
shown by the arrows (fig. 22-4). Because the
position, the first-and-reverse speed main shaft gear is
countershaft second-speed gear and the second-
shifted forward to mesh with and be driven by the
and-third speed main shaft gear are the same size, their
countershaft first-speed gear (fig. 22-3). The countershaft
gear ratio is 1:1. This means that the main shaft rotates
rotates at about 0.7 crankshaft speed. There is a further
at the same speed as the countershaft; that is, the
speed reduction between the countershaft first-speed
engine crankshaft makes about 1.5 revolutions to one of
gear (driving) and the first-and-reverse main shaft gear
the propeller shaft.
(driven) of approximately 1.5. There-fore, the crankshaft
d. High Speed. The third-speed, or direct-drive,
rotates 1.5 x 1.5, or 2.25 times for each turn of the
position of the gears is shown in figure 22-5. In passing
propeller shaft, thus Increasing the torque on the output
from second speed to third speed, the second-and-third
shaft by 2.25:1.
c. Intermediate Speed. The second-speed position is
speed main shaft gear has been shifted forward, causing
the Internal teeth in this gear to engage the external
shown in figure 22-4. In passing from
Figure 22-2. Transmission Gears in Neural Position.


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