TM-9-2520-234-35
POWER TRAIN ASSEMBLY; ALLISON MODEL XTG411-2A
TECHNICAL MANUAL; FIELD AND DEPOT MAINTENANCE MANUAL
JULY 1962
TM-9-2520-234-35 - Page 76 of 323
*C2
CHAP
2,
SEC
V
TORQUE PATH S
PAR
40-4 3
40. HYDRAULIC SYSTEM FUNCTION -
DURING TOW OR PUSH STARTS
OF VEHICLE (fig. 19)
a. When it is necessary to start the ve-
hicle engine by towing or pushing the vehicle
(refer to TM 9-2300-216-10), the manual se-
lector valve must be placed in second gear
position.
b . The function of the hydraulic system
in second gear during a tow- or push -starting
operation is the same as that described for
second gear in par. 32, above, and illustrated
in fig. 8. However, during such an operation
(until the engine begins to rotate), the input
driven pressure pump can not supply main
pressure to the system. The output driven
pressure pump must supply main pressure
until the clutches (output and low range) engage
and until torque is transmitted to the vehicle
engine.
c. The output driven pressure pum p
draws oil, through the sump screen, from the
power train sump. The output of the oil pump
unseats a check valve and flows into the cavity
surrounding the main oil screen assembly.
Thereafter, the oil flow is the same as main
pressure oil flow for second gear under any
other condition.
d . The purpose of the check valve in the
output driven pressure pump output line is to
prevent a back flow of main pressure into the
output driven pump. In neutral, the output
driven pump is not rotating and there is some
loss by leakage through the pump. In reverse
gears, the pump rotates in a reverse direc-
tion and would (except for the check valve)
actually pump oil out of the main pressure
line and return it to the sump.
Section V. TORQUE PATHS THROUGH POWER TRAIN
41. GENERA L
a . Figure 20 is a schematic view of the
power train without the output drive assem-
blies. All of the principal components through
which torque flows are identified. Figure 21
is a cutaway view of the left-output drive as-
sembly, colored to indicate the torque path.
Subsequent figures, 22 through 34, are colored
schematic views, illustrating the torque paths
for the conditions indicated in each view. Ar-
rows on components indicate the direction of
rotation of such components.
b . Explanations of hydraulic action s
under corresponding conditions are in pars.
28 through 40 of this chapter.
c. To avoid needless repetition, refer-
ences are made to preceding explanation s
where applicable.
4 6
42. TORQUE PATH - INPUT TRANSFER
GEARING (fig. 20)
Torque is transmitted from the engine to
the input transfer gearing by a splined coup-
ling shaft. Two idler gears transmit torque
from the input transfer drive gear to the con-
verter cover drive gear. The input rotation
(at coupling shaft) is counterclockwise when
viewed from the left side of the power train.
Rotation of the torque converter is clockwise,
There is a speed increase ratio of 0.611 to
1.000 between the engine and torque converter.
43.
TORQUE PATHS - TORQUE
CONVERTER AND LOCKUP
CLUTCH (fig. 20)
a . Torque is transmitted from the input
transfer gearing to the range gearing by either
the torque converter or lockup clutch. When
the lockup clutch is released, torque is trans-
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