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![]() TM 9-2520-249-34&P
the valve. Pressure at the upper end forces the valve
down, which rapidly expels oil below the valve through
the effect greater pitot pressure has on the downshift
an orifice.
inhibitor valve and lockup shift valve. The position in
(2) In the valve's downward position, the
which these valves are shown can occur any time pitot
lockup circuit is interrupted and the lockup clutch is
pressure is great enough to overcome the opposing
exhausted through a port uncovered by the valve's
forces.
movement. When the shift is completed and the
(1) Downshift inhibitor valve.
Main-
oncoming clutch has been charged, pressure equalizes
pressure from the high-range signal circuit is directed
at each end of the valve. Due to the larger area at the
between the compensator plugs. Movement of the left
lower end of the valve, the valve moves upward and
plug toward the inhibitor valve compresses a spring
resumes the position illustrated. Lockup operation is
between the plug and the valve. This action assists the
restored when the valve moves upward.
pitot pressure in moving the valve plunger into the
e. Fourth-Gear Signal Circuit. Signal pressure
fourth-gear lug.
in this circuit is directed to the pivot valve. In the
(2) Lockup shift value. Pitot pressure
normal steer position, signal pressure in this circuit is
pushes the valve to the upward position. In this
blocked at the pivot valve. However, when the valve
position, main pressure is allowed to flow through the
rotates (350) to the pivot steer position, signal pressure
flow valve to the lockup clutch. The volume of oil to the
is admitted to the bottom of the steer relay valve. The
converter is reduced to that which can flow through the
steer relay valve is forced upward, and pivot steer is
orifice at the left of the valve. This reduced flow
prevented during travel in fourth gear.
provides adequate lubrication and cooling of the
NOTE
converter during lockup operation.
d. Valve.
The related mechanical functions
(1) The function of the flow valve is to
required for this travel condition are
interrupt engagement of the lockup clutch while shifts
described in paragraph 2-50d, and
are being made. During any shift, except to neutral, the
illustrated in figure 2-18.
oncoming clutch is charged with oil which must pass
through the upper orifice. The pressure differential at
the orifice decreases the pressure at the lower end of
2-20
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