What Does a Transmission Shift Solenoid Do?
The role of a transmission shift solenoid is to control the flow of transmission fluid. The transmission control module (TCM) sends an electrical signal telling the shift solenoid when to transfer fluid into and out of the transmission and at what rate. You should know that the shift solenoid’s role varies depending on whether it is in a manual, CVT, or manual transmission.
How a Shift Solenoid Works in an Automatic Transmission
In vehicles equipped with an automatic transmission the shift solenoid shifts the vehicle’s gears for you. Your car’s computer, specifically the transmission control unit, takes information from the engine, speed sensors, and other parts of your car determining the best time to shift gears for power, fuel efficiency, and similar aspects of operation. When the control unit determines that the transmission should be shifted, it sends power or a ground to open the shift solenoid so that transmission fluid can flow into the valve body. This causes the vehicle’s torque converter to change hydraulic pressure enough to shift gears. But because these are electro-mechanical parts, they can fail, making it impossible for your car to shift between gears.
Shift Solenoid Repair and Replacement Cost
The overall cost to replace the shift solenoid in an automatic transmission ranges from $200 to $500 for a single solenoid. If the damage requires you to replace the entire solenoid pack the cost increases to between $250 and $700. Once your mechanic has the part, it should take between 2.5 and 5 hours to replace the solenoid pack and marginally less time to replace a single solenoid.
Will a Bad Shift Solenoid Throw a Code?
Your vehicle’s onboard diagnostics system will throw code P0750 indicating a shift solenoid problem, P0753 for an electrical shift solenoid A fault, P0758 error code indicating an electrical problem with shift solenoid B, and P0977 if there’s a problem with shift solenoid B’s control circuit.
Shift solenoids can be somewhat expensive to replace, but not nearly as much as the entire transmission. Ignoring a warning light or code being thrown by a faulty transmission shift solenoid can lead to serious problems, such as running your vehicle in the wrong gear for your speed and conditions. This can then lead to your transmission overheating and breaking down.
The easiest way to tell is by paying attention to your dashboard warning lights, typically a Check Engine light or Transmission warning light. You may also notice that your vehicle has shifting delays or that it refuses to shift into higher gears altogether. These issues can also be caused by faulty wiring or shorts in your vehicle’s electrical system.
In some situations, a transmission fluid replacement or transmission flush can free up a shift solenoid that has become stuck, helping you avoid higher repair costs. Transmission torque converter replacement could also be an option, depending on what exact parts are malfunctioning. Though it can be tempting to try to repair a bad shift solenoid at home, it’s recommended that you use an experienced shop to diagnose and repair the issue. Why? If the problem is in the wiring, simply replacing the shift solenoid will not fix the problem. In most situations, you’ll need to remove the transmission fluid pan to reach the solenoid, and in some vehicles, you’ll need to replace the entire solenoid pack to fix the problem. You’ll also need to replace the transmission filter and fluid at the same time.
Signs of a Bad Transmission Shift Solenoid
- Delay shifting upon acceleration and deceleration
- Your transmission is stuck in neutral
- Rough shifting
- Engine revs loudly even when you apply the brakes
- Your transmission cannot downshift and the engine is loud
If you’re concerned that recent loss of power in your vehicle may be related to issues with your shift solenoids or your transmission in general, it’s important to have the problem investigated quickly before more damage can take place. Proper diagnosis is especially important if the check engine light is on.
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