Overdrive Range, 3-2 Downshift

Overdrive Range - 3-2 Downshift:

During all full throttle downshifts, the engine manifold vacuum supply to the vacuum modulator (32) drops. This allows the modulator valve (34) to move and to increase the modulator pressure to the line boost valve (304). At the same time, the pump output increases through the higher engine speeds. This forces a higher volume of fluid into the line circuit. The increased pressure of the modulator fluid and the increased volume of fluid at the pressure regulator valve (313) create higher line pressures for proper clutch and valve operation. A full throttle 3-2 downshift occurs when the Powertrain Control Module (PCM)receives input signals from the VS Sensor and the TP Sensor in order to energize (turn ON) the 2-3 shift solenoid valve (315). Line pressure at the solenoid is forced into the 2-3 shift solenoid passage, and the pressure is directed to the 4-3 manual downshift valve (360) and to the 3-2 manual downshift valve (356). The 2-3 shift solenoid valve fluid forces the 3-2 manual downshift valve (356) to move. This also shifts the 2-3 shift valve (357). Line pressure at the 2-3 shift valve (357) is now directed into the input clutch feed passage, through the 3-4 shift valve (362) into the input clutch passage. Input clutch fluid seats the #3 checkball (372) and the fluid applies the input clutch. The third clutch is released by allowing third clutch/Lo-First fluid to exhaust through the #4 checkball (372) and into the third clutch passage. Third clutch fluid is directed to the #9 checkball (372) forcing the fluid through the exhaust orifice and into the third fluid passage to the 2-3 shift valve (357), where the fluid exhausts.

MODULATOR VALVE (34)
The modulator valve moves in response to the engine manifold vacuum. The valve increases modulator pressure to the line boost valve (304).

LINE BOOST VALVE (304)
The line boost valve moves in response to the modulator pressure. The valve increases line pressure through the pressure regulator valve (313).

PRESSURE REGULATOR VALVE (313)
The pressure regulator valve increases line pressure in response to increased modulator pressure.

2-3 SHIFT SOLENOID VALVE (315)
The 2-3 shift solenoid valve energizes, allowing line pressure into the 2-3 shift solenoid valve passage in order to force a 3-2 downshift.

4-3 MANUAL DOWNSHIFT VALVE (360)
The 2-3 shift solenoid valve fluid shifts the 4-3 manual downshift valve. This shifting prevents the 3-4 shift valve (362) from moving.

3-2 MANUAL DOWNSHIFT VALVE (356)
The 2-3 shift solenoid valve fluid shifts the 3-2 manual downshift valve in order to downshift the 2-3 shift valve (357).

2-3 SHIFT VALVE (357)
When the 2-3 shift valve is downshifted, line pressure enters the input clutch feed passage. The valve also directs the line pressure to the 3-4 shift valve (362).

3-4 SHIFT VALVE (362)
The 3-4 shift valve directs input clutch feed fluid into the input clutch passage, and then the valve sends the fluid to the #3 checkball (372).

#3 CHECKBALL (372)
The #3 checkball is located in the channel plate (400). The checkball is seated against the PRN passage in order to allow input clutch fluid to apply the input clutch.

#4 CHECKBALL (372)
The #4 checkball is located in the channel plate (400). The checkball directs third clutch/Lo-First exhaust fluid into the third clutch passage.

#9 CHECKBALL (372)
The #9 checkball is located in the valve body (300). The checkball directs third clutch exhaust fluid into the third fluid passage. Third fluid is then sent to the 2-3 shift valve (357), where the fluid exhausts.