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627333-A 3-13 Transmission and Solenoids Schematic of modulating valve (transmission) 1. Modulating Valve (Transmission); 2. Test Port; 3. Transmission Clutch; 4. Spring; 5. Line to Sump; 6. Spool Orifice; 7. Charge Pressure Oil; 8. Solenoid. Modulating valve (1) is controlled by transmission electronic control module (ECM). The modulating valve is used by the transmission ECM to directly modulate the oil pressure that is sent to each of the nine individual transmission clutches. When the operator selects a direction or when the operator selects a speed, the transmission ECM sends a pulse width modulated signals in order to vary the current to solenoid (8). The distance that is travelled by the solenoid plunger is proportional to the electrical current that is sent to the solenoid. The position of the solenoid plunger controls the oil pressure the is sent to transmission clutch (3). When the transmission ECM sends the maximum programmed current to the modulating valve, the pressure in the transmission clutch will be at the maximum desired pressure. When no current is sent to the modulating valve, the oil pressure in the transmission clutch will be zero. FIG. 13 Q000038S 2 3 4 5 1 8 7 6 |