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 68 of 323
CHAP
2,
SEC
I V
OPERATION OF HYDRAULIC SYSTEM S
PAR
3 7
feed pressure. Maximum downward movement
will produce maximum steer feed pressure.
(3) Right-steer feed pressure flows to
the steer relay valve which directs it to the
right brake.
The clutch-brake method is used
for first-gear steer. In right steer, the right
brake is applied. Full-right steer stops the
right output of the power train. Partial-right
steer slows the right output.
(4) Upward movement of the left-steer
valve does not interrupt the flow of steer pres-
sure
to
the
left-drive
clutch
(geared
steer
clutch). This upward movement, however ,
does open a passage through which oil can
flow, through an orifice, to the steer coolant
feed line. The steer coolant feed line carries
oil to the steer relay valve, where it is sent to
the right brake, through the clutch-brake steer
coolant line.
(5) A ball-type check valve is located
between each of the steer feed lines and steer
coolant feed lines. The upper check valv e
opens when the application of right steer is
discontinued, and allows the brake apply pres-
sure to exhaust through the clutch-brake steer
coolant line.
(6) In right steer in first gear, the right-
drive clutch (geared steer clutch) is released,
the right brake is applied and cooled, and the
left-drive clutch (geared steer clutch) remains
engaged and continues to drive.
b. Second Gear, Full-left Steer
—
(fig. 14)
Note . Refer to par. 54 and fig. 30
for the torque path through the power
train.
(1) The hydraulic system will function
in second gear steer in the same manner as
described for second-gear straight travel in
par. 32, above, except for the position of the
steer valves and the flow of oil to the drive
clutches and brakes.
(2) In left steer, the steer control shaft
is rotated counterclockwise. This rotatio n
moves the right- steer valve upward while, the
left-steer valve moves downward. Flow to the
left-drive clutch (output clutch) is blocked. A
regulated steer feed pressure is sent to the
steer relay valve. The steer relay valve sends
oil to the left brake through the left-brake
apply line.
(3) The flow to the right-drive clutch
(output clutch) is not interrupted and the clutch
continues to drive the right output. The right-
steer valve supplies steer coolant feed to the
left brake. The left-brake apply pressure can
exhaust through the lower check valve (between
steer feed and steer coolant feed lines) and the
clutch-brake steer coolant line, when applica-
tion of steer is discontinued.
38. HYDRAULIC SYSTEM FUNCTION –
THIRD AND FOURTH GEARS, STEER
a. Third Gear, Full-right Steer
—
(fig. 15)
Note . Refer to par. 55 and fig. 31
for the torque path through the power
train.
(1) The hydraulic system will function
in third-gear steer in the same manner as de-
scribed in par. 33, above, except for the posi-
tion of the steer valves and the flow of oil to
the drive clutches and steer clutches.
(2) Downward movement of the right-
steer valve and the resulting oil flow is de-
scribed in par. 37a(2), above.
—
(3) Right-steer feed pressure flows to
the steer relay valve which directs it to the
right- geared steer clutch, through the geared
steer clutch apply line .
The geared steer
method is used in third-gear steer. In right
steer, the right-geared steer clutch is applied.
Full-right steer fully applies the steer clutch
so that no slippage occurs. Partial-right steer
allows the steer clutch to slip somewhat.
(4) Upward movement of the left-steer
valve does not interrupt the flow of steer pres-
sure to the left-drive clutch (output clutch).
This upward movement, however, does open
a passage through which oil can flow, through
an orifice, to the steer coolant feed line. The
steer coolant feed line carries oil to the steer
3 8
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