Case 580SR, Service Manual

Page: 182 / 1068

116 SECTION 21 - TRANSMISSION
The range clutches also have modulation which op-
erates as follows:
When the range is changed, oil will flow through the
modulation shift spool to the chosen range clutch
momentary until the friction discs are closed against
the dished plate. At that moment the range modula-
tion solenoid is activated. The pilot pressure will
move the modulation shift spool so that oil supply is
fed through a restrictor which is in by-pass of the
valve. The controlled volume of oil is used to push in
the dished outer plate gradually until the clutch is ful-
ly closed.
This will give a smooth build up of torque. At that mo-
ment the range modulation solenoid is released, so
that the modulation shift spool return to its rest posi-
tion and allowing full oil flow to the clutch. The control
valve also controls the front lower output disconnect
clutch. If the solenoid is not activated full oil pressure
is fed through the disconnect shift spool to the dis-
connect clutch. If the solenoid is activated, pilot pres-
sure will move the disconnect shift spool to block oil
supply to the disconnect clutch to release it. The con-
trol valve also has a speed sensor. This sensor will
pick up upper output gear speed.
This information is used in the electronic gear selec-
tor to determine shift logic.
Since the sensor picks up upper output gear speed,
the signal will be in direct relation of the turbine
speed if any directional clutch is engaged.
Transmission gear Activated solenoids Activated clutches
Forward 4 Forward Forward high, 2nd
Forward 3 Forward, 2nd/1st Forward high, 1st
Forward 2 Forward, forward high/low Forward low, 2nd
Forward 1 Forward, forward high/low, 2nd/1st Forward low, 1st
Reverse 1 Reverse, 2nd/1st Reverse, 1st
Reverse 2 Reverse Reverse, 2nd
Disconnect off Disconnect ---------------
Disconnect on --------------- Disconnect
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