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Home >> Buick >> 2007 >> Lucerne CX >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 2 (Automatic Transaxle - 4T80-E - Introduction (2 Of 2)) >> Description and Operation >> Automatic Transmission Hydraulic Diagrams >> Overdrive Range, Fourth Gear >> Fourth Band Applies

Fourth Band Applies

WARNING: This page is about a different variant/trim than selected.

1-2 Shift Solenoid (SS) Valve 

The PCM energizes (turns ON) the 1-2 SS valve. The PCM blocks the exhaust of 1-2 SS valve fluid to create high fluid pressure within the valve. High pressure at the 2-3 shift solenoid (SS) valve, at the end of the 1-2 shift valve, holds the valve in the upshifted position, while fluid from the 1-2 SS valve is routed to the end of the 3-4 shift valve.

3-4 Shift Valve 

High fluid pressure in the 1-2 SS valve moves the 3-4 shift valve to the upshifted position. The 3-4 shift valve allows orificed third clutch fluid to enter the fourth band feed passage. Fourth band feed is then routed to the 1-2 shift valve.

1-2 Shift Valve 

High fluid pressure in 2-3 shift solenoid (SS) valve holds the 1-2 shift valve in the upshifted position. The 1-2 shift valve allows fourth band feed fluid to enter the fourth band circuit. Fourth band fluid is then routed to the 3-4 accumulator piston and to the fourth servo piston.

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