What Is A Transmission Solenoid?

January 14, 2021 | By Mister Transmission

What Is A Transmission Solenoid?

The “transmission solenoid”. Or maybe you heard it as “solenoid pack”. Drivers often hear of this for the first time when something’s gone wrong with it. But just what is a transmission solenoid?

What Is A Transmission Solenoid?

The transmission solenoid is a type of electromechanical valve that controls the flow of fluid. Specifically, in an automatic transmission, we mean the flow of automatic transmission fluid into and through the transmission. In modern transmissions, the transmission solenoid generally comes in a pack which is installed in the transmission control unit, the transmission control module, or a transmission valve body. Transmission fluid is critical to the function of the transmission. If its flow is impeded or hindered, your transmission cannot operate properly.

How Does The Transmission Solenoid Work?

Transmission solenoids are powered by an electrical current supplied by the transmission controller or computer. This is how it works: the transmission computer sends out instructions to the individual transmission solenoids in the pack which then direct transmission fluid to specific clutch packs or servo valves in order to control gear shifting to suit the given driving conditions and engine requirements. A transmission solenoid generally consists of nine parts that all must work together in order for your transmission to properly operate. The nine common parts are:

  • The valve body
  • An inlet port
  • An outlet port
  • The solenoid coil body
  • The coil winding
  • Lead wires
  • A plunger or piston
  • A spring
  • An orifice

What Does A Transmission Solenoid Look Like?

The solenoid body is generally made of steel and it has a cylindrical shape. Transmission solenoids have a valve and return spring in them. The solenoid coil consists of wire wound around a conductive component that acts as an electronic magnet. Controlling the valves position.  

What Happens When A Transmission Solenoid Goes Haywire?

If your transmission solenoid is not operating properly, you are going to have problems shifting. Often this is caused by an electrical malfunction. When this happens, the transmission solenoid acts erratically. In modern vehicles, an electrical or computerized problem should result in the Check Engine light illuminating. However, this is less likely if you are dealing with a mechanical failure.

What Are The Symptoms Of A Transmission Solenoid Problem?

Some common transmission solenoid problems include:

  • A Delay in Shifting
    A common delay will only be a few seconds, but it can be as long as over a minute.
  • The Transmission Refuses to Downshift
    A properly functioning transmission automatically downshifts as it slows down. With a malfunctioning solenoid, however, your transmission might downshift uncontrollably or not at all.
  • The Transmission Shifting into the Wrong Gear
    A defective solenoid can cause your transmission to shift into an incorrect gear.

Mister Transmission

Please contact us to learn more about transmission solenoids.

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I just wanted to say that the Orillia Mr T is amazing! Christina is very pleasant to deal with. They tested my car and told me the power issue and engine light was an engine problem and that the transmission was in good shape. They also said it was probably a turbo related problem. I had my mechanic fix the issue which was a cracked air intake pipe for the turbo. It's great to deal with a very professional and honest operation!
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