Case 580SR Service Manual page 83

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OIL FLOW SOLENOID CONTROL VALVE OPERATION (FORWARD DRIVE ONLY SHOWN)
The solenoid valve when in neutral position dead
heads the oil flow at the spool (1) from the supply
port and no oil is allowed to pass through the valve.
Therefore the oil in the galleries beyond the spool at
the fill time metering valve (2) remains static.
Selection of the forward / reverse powershuttle lever
in the cab directs a current flow to the forward or re-
verse solenoid and the spool (1) will move in the di-
rection selected, reverse shown. The oil then flows
past the spool to the clutch pack and applies pres-
sure to the fill time metering valve (2), a small bore
allows oil to flow into the clutch feathering valve.
When valve (2) moves it partially uncovers a port to
the tank and also opens the control orifice within the
valve. Therefore a precisely metered flow of oil is fed
to the pressure regulating (feathering) piston (3). As
this piston is pushed back against its spring the pres-
sure at the clutch builds up gradually to give a
smooth jerk free clutch engagement.
When the piston reaches the end of its travel, clutch
pressure quickly builds up to full system pressure ei-
ther side of valve (2) so the light spring pushes the
valve covering the port to the tank.
The oil is dead headed at system pressure at the
clutch so ensuring full torque can be transmitted by
the clutch.
NOTE: the control valve also includes a pressure
regulating (feathering) valve and a fill time metering
valve for the reverse clutch pack.
SECTION 21 - TRANSMISSION
3
3
3
Regulated pressure oil
Return oil
Pressure oil
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F29975
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F29976
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F29977