A transmission shift solenoid is what controls the flow of transmission. This is done through a module that sends an electrical signal telling the shift solenoid exactly when to transfer fluid in and out of the transmission along with the right rate. The role of a shift solenoid will vary based on the type of transmission and whether it is in a manual, continuously variable or automatic one.

If your car has an automatic transmission, the shift solenoid will shift the gears for you. The transmission control unit will take the information from the engine and speed sensors along with other parts of your vehicle to then decide when to shift gears for power and fuel efficiency. It will determine the ideal time the transmission should be shifted and the control unit will send power to open the shift solenoid to allow transmission fluid to flow into the valve body. This is what causes the torque converter in the car to change hydraulic pressure to the point where it can shift gears.

If you see a warning light pointing to an issue with your transmission shift solenoid, it’s important to visit a mechanic right away; otherwise, it can lead to far more serious problems that will be very expensive to fix. Replacing a shift solenoid is not nearly as costly as the replacement fee of the entire transmission and getting it fixed will prevent issues like your vehicle running in the wrong gear for your speed and conditions, or your transmission overheating and breaking down. Pay attention to your dashboard so that you don’t run into these problems and if you notice that your car is experiencing shifting delays or completely refusing to shift into higher gears, it’s definitely a sign of a problem that requires immediate attention.

Rough shifting, delayed shifting when accelerating or decelerating, the transmission is stuck in neutral and your engine revving loudly when you brake are all signs of a faulty transmission shift solenoid that should be looked at right away. A transmission fluid replacement or flush may clear up a shift solenoid that has become stuck, although this may not apply to every situation.

The reason a professional technician is required is that the problem may be with the wiring, in which case a simple replacement of the shift solenoid will not solve the issue. A mechanic can assess the situation by removing the transmission fluid pan to reach the solenoid, after which they can replace the entire solenoid pack to fully resolve the problem. They can also replace the transmission filter and fluid for you as well.