TM-5-3805-254-14-P-2
TRUCK, DUMP, 20 TON, 6X4, ON-OFF HIGHWAY 71,000 GVW, IHC MODEL F-5070 (CCE)
TECHNICAL MANUAL; OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT, GENERAL SUPPORT AND DEPT MAINTENANCE MANUAL (INCLUDING REPAIR PARTS INFORMATION AND SUPPLEMENTAL MAINTENANCE INSTRUCTIONS)
JUNE 1980
TM-5-3805-254-14-P-2 - Page 694 of 894
TRUCK SERVICE MANUAL
HT 700D SERIES TRANSMISSIONS
before going to the cooler.
A flow of air or water over or
through the cooler removes the heat from the
transmission oil.
(3)
Lubrication oil (green) is directed through
the transmission to components requiring continuous
lubrication and cooling.
The lubrication oil then drains
into the sump.
Oil in excess of that required by the
lubrication circuit escapes to the sump through the
lubrication regulator valve.
f. Selector Valve, Forward
Regulator Circuits (foldouts
5,
)
(2)
THE SELECTOR VALVE
can be shifted
into seven lever positions; (R) reverse, (N) neutral, (D5)
drive 5, (D4) drive 4, (D3) drive 3, (D2) drive 2, (D1) drive
1.
Attach of these positions, the selector valve
establishes the hydraulic circuit for operation in the
condition indicated.
NOTE
The quadrant
designations listed above
are not necessarily the same as those in
the vehicle.
(4)
drive 1, drive 2, drive 3, drive 4 and drive 5
are forward ranges.
Anytime the vehicle moves forward,
regardless of what range was selected, it starts in first
gear.
Shifting is automatic in any of the above ranges,
varying with vehicle speed and throttle position.
(6)
The forward regulator pressure i s directed
from the selector valve to the main-pressure regulator
valve when the selector valve is in any position except
reverse.
In neutral and all forward drive ranges, this
regulator pressure assists the pump pressure acting
downward upon the main pressure regulator valve.
In
reverse, the neutral-forward pressure is absent from the
main-pressure regulator valve.
This allows the valve
spring to exert its full force upward against the regulator
valve, causing an increase in main pressure.
This
increase in pressure is necessary for higher clutch
pressures, to handle the high torque produced in reverse
gear.
g. Rear Governor Circuit
(1)
Governor feed is merely main pressure
directed to the governor valve.
A centrifugal-type g o v e
r n o r, driven by the transmission output, controls the
position of the governor valve.
The position of the
governor valve determines the pressure in the governor
circuit.
When the transmission output is not rotating,
governor pressure is negligible.
When the transmission
output rotates, governor pressure varies with the speed
of rotation.
(2)
Governor pressure is directed to the shift
signal valves and to the governor accumulator valve.
(3)
The governor accumulator valve is a
spring-loaded valve in a straight bore.
The accumulator
valve absorbs pressure surges and provides a more
uniform governor pressure.
h. Modulator Pressure Circuit
foldouts
5,
)
(1)
The
modulator
valve
produces
a
regulated, reduced pressure which is derived from main
pressure.
The valve is moved rightward by a spring at
the left end of the valve when the throttle is closed.
The
valve is moved leftward by the cam and spring action
when the throttle is opened.
When the spring force at
the left of the valve is imbalance with the spring force
and modulator pressure at the right end of the valve,
modulator pressure is regulated.
(2)
When the throttle setting is increased, the
upward (or downward) movement of the actuator cam
forces the modulator valve toward the left.
This leftward
movement reduces modulator pressure.
When the
throttle setting is reduced, the downward movement of
the actuator cam allows t he spring at the left end of the
valve to return the valve to another regulating position.
Because the throttle setting is varied w it h load and
engine speed, modulator pressure varies also.
(3)
At all the shift signal valves, modulator and
governor pressures act on calibrated areas to upshift the
valves against
687
TRANSMISSION
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