How do Transmission Solenoids Work?

What are Transmission Solenoids?

Automatic transmissions rely on solenoids to make gear changes easier. Solenoids are electro-hydraulic valves that control one or more gears in conjunction with the car's transmission and construction. Through opening or closing based on electrical signals, they control the flow of transmission fluid when a solenoid opens or closes, it shifts the friction within the engine, causing the car to change gears. Automatic transmissions depend on the vehicle's speed sensors and the Engine Control Unit (ECU) or Transmission Control Unit (TCM) to measure the vehicle speed and signal the necessary changes, including control of transmission solenoids to adjust the gears of your vehicle.


How do solenoids in a transmission work?

Within the engine of your vehicle, the speed sensors constantly monitor how your car runs and determine what needs to be adjusted. It includes knowing when your car has to change gears to get the right power and speed, either up or down. When changes need to be made, the speed sensors can work with the ECU or TCM to send signals to parts of your vehicle, like telling transmission solenoids when to open or close so your car can change gears.


There is a spring-loaded plunger inside the transmission solenoids that is wrapped in a wire connected to the speed sensors and ECU or TCM. The wire is how they transmit signals within the transmission to regulate the flow of hydraulic fluid. The required clutches and bands are pressurized by the solenoids that adjust the transmission fluid flow and allow a smooth transition between gears so that you can continue to accelerate.


Some Signs of Transmission Solenoids problems can be

Delayed or Erratic Gear Changing If you find that changing gears takes a little longer for your vehicle, it may be a defective solenoid. Dirty transmission fluid can trigger solenoids to remain open or closed, making it harder for your transmission to change gears when necessary.


Your Transmission gets stuck in Neutral another indication that you have one or more solenoids stuck open or closed because of the filthy transmission fluid. While the solenoid receives the signal to switch into the first gear, the necessary action cannot be performed.


Your Check Engine Light Comes On This is a sure sign that you need to carry your car to a diagnostic repair shop. Also, if you reach the point where your inspection engine light is on, your transmission may go into limp or Fail Safe mode, which means you're going to have even more trouble driving your car. You will have limited power and gears available so the way your car drives will change noticeably.