Overdrive Range - 3-2 Downshift

Overdrive Range - 3-2 Downshift:

OVERDRIVE RANGE - 3-2 DOWNSHIFT

"A" SHIFT SOLENOID - OFF
INPUT CLUTCH - APPLIED
1/2 SUPPORT ROLLER CLUTCH - HOLDING
"B" SHIFT SOLENOID - ON
INPUT SPRAG - OVERRUNNING
FORWARD BAND - APPLIED
SECOND CLUTCH - APPLIED

During all full throttle downshifts, engine manifold vacuum supply to the vacuum modulator (32) drops allowing the modulator valve (34) to move and increase modulator pressure to the line boost valve (304). At the same time, pump output increases through the higher engine speeds forcing a higher volume of fluid into the line circuit. The increased modulator fluid pressure and increased volume of fluid at the pressure regulator valve (313) creates higher line pressures for proper clutch and valve operation. A full throttle 3-2 downshift occurs when the PCM receives input signals from the VS sensor and TP sensor to energize" or turn on "B" shift solenoid (315). Line pressure at the solenoid is forced into the "B" shift solenoid passage and is directed to the 4-3 manual downshift valve (360) and 3-2 manual downshift valve (356). "B" shift solenoid fluid forces the 3-2 manual downshift valve (356) to move also shifting 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 #3 checkball (372) and applies the input clutch. The third clutch is released by allowing 3rd clutch/lo-1st fluid to exhaust to the #4 checkball (372) and into the 3rd clutch passage. 3rd clutch fluid is directed to #9 checkball (372) forcing it through the exhaust orifice and into the 3rd fluid passage to the 2-3 shift valve (357) where it exhausts.

Modulator Valve (34): Moves in response to engine manifold vacuum and increases modulator pressure to the line boost valve (304).

Line Boost Valve (304): Moves in response to modulator pressure to increase line pressure through the pressure regulator valve (313).

Pressure Regulator Valve (313): Increases line pressure in response to increased modulator pressure.

"B" Shift Solenoid (315): Energizes, allowing line pressure into the "B" shift solenoid passage to force a 3-2 downshift.

4-3 Manual Downshift Valve (360): Is shifted by "B" shift solenoid fluid and prevents the 3-4 shift valve (362) from moving.

3-2 Manual Downshift Valve (356): Is shifted by "B" shift solenoid fluid to downshift the 2-3 shift valve (357).

2-3 Shift Valve (357): When downshifted, it allows line pressure to enter into the input clutch feed passage and directs it to the 3-4 shift valve (362).

3-4 Shift Valve (362): Directs input clutch feed fluid into the input clutch passage and sends it to the #3 checkball (372).

#3 Checkball (372): Located in the channel plate (400), it is seated against the PRN passage to allow input clutch fluid to apply the input clutch.

#4 Checkball (372): Located in the channel plate (400), it directs 3rd clutch/lo-1st exhaust fluid into the 3rd clutch passage.

#9 Checkball (372): Located in the valve body (300), it directs 3rd clutch exhaust fluid into the 3rd fluid passage. 3rd fluid is sent to the 2-3 shift valve (357) where it exhausts.