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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 132 (Automatic Transmission - 4L60-E/4L65-E/4L70-E - Introduction (2 Of 2)) >> Description and Operation >> Automatic Transmission Hydraulic Diagrams >> Overdrive Range, 4-3 Downshift >> Notes

Overdrive Range, 4-3 Downshift: Notes

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When the transmission is operating in fourth gear, a forced 4-3 downshift occurs if there is a significant increase in throttle position. At minimum throttle, the vehicle speed decreases gradually (coastdown) and the PCM commands a 4-3 downshift. The PCM also initiates a forced 4-3 downshift when the throttle position remains constant but engine load is increased, such as driving up a steep incline. To achieve a 4-3 downshift, the PCM de-energizes the 1-2 shift solenoid valve and the following changes occur to the transmission's electrical and hydraulic systems:

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