Case 580SR Service Manual page 193

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CONTROL VALVE OPERATION FORWARD, THIRD GEAR WITH 4WD DISENGAGED
Pressure oil from the system regulating valve flows to the pressure reducing valve.
The pressure lowers to 5.5 bar. This oil flows to the 6 solenoids. Oil also supplies the modulation valve.
When the powershift lever is moved forward and twisted anti clock wise and the 4WD is switched off a electrical
signal is sent to:
Z The 4WD solenoid supplies pilot oil to the shift spool.
This will move the spool preventing oil flowing to the clutch disengaging 4WD.
Z The range modulation solenoid allowing pilot oil to the range modulation valve, which restricting oil flow to the
1st 2nd shift spool.
Z The 1st 2nd solenoid, sending pilot pressure to the 1st 2nd shift spool which directs oil to the 1st clutch.
Z Once the 1st gear clutch is engaged the range solenoid is de-energized and full flow will go to the 1st gear
clutch.
Z The neutral forward solenoid which energizes allows pilot pressure to flow to the shift spool this will allow oil
to flow on to the forward high shift spool.
Z The modulation valve has a reducing current from the microprocessor, pilot pressure gradually increases act-
ing on the boost valve and it multiplies pilot pressure by 4.
The oil from the boost valve is modulated allowing a steady increase of pressure to act on the forward high
clutch pack which gradually takes up drive until clutch pressure reaches 20 bar.
1. Transmission sump
2. Transmission breather
3. Suction strainer
4. Gerotor oil pump
5. Pressure oil filter
6. Filter by-pass valve 4.3 bar
7. System pressure test port
8. System pressure regulating valve 20 bar
9. Oil to converter system
10. Pressure reducing valve 5.5 bar
11. 2nd/1st Solenoid
12. 2nd/1st shift spool
13. 2nd gear clutch
14. 1st gear clutch
15. Range modulation solenoid
16. Range modulation spool
17. Range modulation restriction
18. 4WD solenoid
19. 4WD shift spool
20. 4WD clutch
21. High/low solenoid
22. High/low shift spool
23. Forward high clutch
24. Forward low clutch
25. Neutral reverse solenoid
26. Neutral reverse shift spool
27. Reverse clutch
28. Neutral forward solenoid
29. Neutral forward shift spool
30. Electronic modulation valve 0-5.5 bar
31. Accumulator
32. Pressure booster 0-20 bar
SECTION 21 - TRANSMISSION
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