Case 580SR Service Manual page 189

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SERVO CONTROL FORWARD THIRD GEAR 4WD ENGAGED
System pressure is reduced to 5.5 bar by the pressure reducer this oil then supplies the 6 solenoids and elec-
tronic modulation valve.
Z When the powershift lever is moved forward and twisted anti clockwise an electrical signal is sent to:
Z The range modulation solenoid sending pilot pressure to the spool.
Z The 1st 2nd solenoid sending pilot pressure to the spool.
Z Once the 3rd gear has been engaged the range modulation solenoid will be de-energized.
Z The high/low solenoid prevents pilot oil to flow to the shift spool.
Z The neutral forward solenoid allowing pilot oil to flow to the shift spool.
Z The powershift electronics will then reduce the current to the modulation valve which gives an output pressure
curve from 0-5.5 bar to the pressure booster valve.
Z The modulation pressure curve is multiplied by 4 in the pressure booster so that a curve of 0-20 bar is avail-
able for the directional clutch.
Between the modulation valve and the booster is accumulator to dampen any hydraulic vibration.
Z The 4WD solenoid supplies pilot oil to the shift spool.
Suction oil
High pressure oil
Torque Converter and Lubrication Oil
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 20 bar
8. System pressure regulating valve 20 bar
9. Oil flow to converter
10. Oil flow to shift spools
11. Pressure reducing valve 5.5 bar
SECTION 21 - TRANSMISSION
12. 2nd/1st Solenoid
13. Range modulation solenoid
14. 4WD solenoid
15. High/low solenoid
16. Neutral reverse solenoid
17. Neutral forward solenoid
18. Electronic modulation valve 0-5.5 bar
19. Accumulator
20. Pressure booster 0-20 bar
21. Modulated pressure to shift spools 0-20 bar
Return to oil tank
Pilot pressure
Modulated pilot oil
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