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A transmission solenoid or cylinoid is an electro-hydraulic valve that controls fluid flow into and throughout an automatic transmission. Solenoids can be normally open or normally closed. They operate via a voltage or current supplied by the transmission computer or controller.
By activating and deactivating the solenoids in a predetermined pattern by the PCM, 4 distinct gear ratios can be achieved. The last 4L60Es were only used in the GM Vans in 2013, before being replaced by the 6L80E. The shift solenoid pattern, also sometimes referred to as solenoid firing order, is as follows; Shift Solenoid Pattern
The 4L80-E uses two shift solenoids, initially called Shift Solenoid A and Shift Solenoid B; they were later changed to comply with OBD-II regulations to 1-2 shift solenoid and 2-3 shift solenoid. By activating and deactivating the solenoids in a predetermined pattern by the PCM, four distinct gear ratios can be achieved.
Newer automatic transmission designs often use many pressure control solenoids, and sometimes allow the shift solenoids themselves to provide precise pressure control during shifts by ramping the solenoid on and off. The shift pressure affects the shift quality (too high a pressure will result in rough shifting; too low a pressure will cause ...
It lets the PCM know what the torque will be in the next gear so it can choose the shift points based on the vehicle's projected performance in the next gear. Coupled with the electronic throttle strategy, the transmission computes the output torque required to maintain the vehicle speed and chooses the correct gear and converter state accordingly.
The solenoid pack is mounted directly to the valve body; its connector protrudes from a hole on the left side of the transmission. On the 45 and 545RFE the hydraulic control system design (without electronic assist) provides the transmission with PARK, REVERSE, NEUTRAL, SECOND, and THIRD gears, based solely on driver shift lever selection.
Unlike the A140E counterpart which is electronically controlled, the A140L uses a plastic governor gear to select which gear to go into. Over time and wear, this plastic gear's teeth shred and eventually cease to be able to control gears. This results in a transmission that can only shift to first and reverse, but not to any further forward gears.
Pushing a button on the shift control preselected the chosen gear. The electrical circuit was closed only after the driver fully depressed the clutch pedal. This energized the appropriate transmission mounted solenoids necessary for returning the transmission to neutral and then completing engagement of the preselected gear.