K 1500 Suburban 4WD V8-5.3L VIN Z Flex Fuel (2003)
Shift Solenoid: Description and Operation
4L60-E/4L65-E
4L60-E/4L65-E
1-2 and 2-3 Shift Solenoid Valves
The 1-2 and 2-3 shift solenoid valves (also called A and B solenoids) are identical devices that control the movement of the 1-2 and 2-3 shift valves (the
3-4 shift valve is not directly controlled by a shift solenoid). The solenoids are normally-open exhaust valves that work in four combinations to shift the
transmission into different gears
The PCM energizes each solenoid by grounding the solenoid through an internal quad driver. This sends current through the coil winding in the solenoid
and moves the internal plunger out of the exhaust position. When ON, the solenoid redirects fluid to move a shift valve.
Important: The manual valve hydraulically can override the shift solenoids. Only in D4 do the shift solenoid states totally determine what gear the
transmission is in. In the other manual valve positions, the transmission shifts hydraulically and the shift solenoid states CATCH UP when
the throttle position and the vehicle speed fall into the correct ranges.
The PCM-controlled shift solenoids eliminate the need for TV and governor pressures to control shift valve operation.
3-2 Shift Solenoid Valve Assembly
The 3-2 shift solenoid valve assembly is a normally-closed, 3-port, ON/OFF device that is used in order to improve the 3-2 downshift. The solenoid
regulates the release of the 3-4 clutch and the 2-4 band apply.
