Gear issues driving you crazy?
Got a sluggish vehicle, too?
Sounds like your transmission solenoid is the culprit.
Faulty transmission shift solenoids lead to delayed gear shifting, skipping gears, and gears getting stuck — making your car dangerous to drive.
To keep you safe on the road, we’ll take you through transmission solenoid replacement and diagnosis. We’ll also cover the costs and best maintenance practices to keep your vehicle running smoothly.
Let’s begin.
This Article Contains:
- What Is a Transmission Solenoid and What Does It Do?
- 3 Symptoms of a Faulty Transmission Solenoid
- How to Diagnose and Replace a Faulty Transmission Solenoid
- How Much Does a Transmission Solenoid Replacement Cost?
- 3 FAQs on Transmission Solenoid
What Is a Transmission Solenoid and What Does It Do?
A transmission solenoid is an electro-mechanical valve that controls the flow of transmission fluid. This helps in gear lubrication and operation on automatic transmission vehicles (manual transmission cars don’t have transmission solenoids).
Although several parts contribute to its functioning, its primary components include the solenoid body, valve, return spring, and coil.
How does it work?
When changing gears, the transmission control unit signals the solenoid to open, allowing transmission fluid to enter the valve body. This engages the torque converter, which uses this hydraulic pressure to shift to the correct gear.
Modern vehicles have several solenoids:
- Shift solenoid: The transmission shift solenoid helps engage gears by regulating the flow of transmission fluid. Shift solenoids play an essential role in the smooth operation of the transmission system.
- Transmission control solenoid: Regulates the pressurized hydraulic fluid (line pressure).
- Torque converter clutch solenoid: This controls the torque converter lockup clutch, a component that enables a direct mechanical link between the engine and transmission.
Now that you know about transmission solenoids, let’s discover what happens when they go bad.
3 Symptoms of a Faulty Transmission Solenoid
Here’s what to expect if a transmission solenoid breaks:
1. Gear Issues
A faulty shift solenoid causes several gear-related issues:
- Delayed gear shifting: A faulty shift solenoid may not provide enough hydraulic pressure to shift gears at normal speed.
- Skipping gears: A lack of pressurized hydraulic fluid (line pressure) on automatic transmission vehicles may prevent the correct gear from engaging.
- Getting stuck in certain gears: If the solenoid valve gets stuck, it won’t provide the pressure necessary for a gear change.
2. Vehicle Sluggishness
If a transmission solenoid breaks, the electronic control unit (ECU) on some vehicles may activate the “limp mode.” This limits your engine RPMs and driving gear (on automatic transmission vehicles) to prevent damage to other car parts.
3. Illuminated Check Engine Light
When the ECU detects a problem with the transmission solenoid, it’ll trigger the check engine light. However, this doesn’t mean you need an engine repair. It can indicate several problems.
You can use an OBD-II scanner to detect the code associated with the specific transmission problem. An example is the P0750 (shift solenoid) code.
Want to confirm if you have a transmission solenoid problem?
Let’s look at the diagnostic and replacement processes.
How to Diagnose and Replace a Faulty Transmission Solenoid
Diagnosing and replacing a faulty transmission solenoid is complicated, so it’s best to have a mechanic handle it.
To diagnose a transmission solenoid problem, they’ll:
- Read the diagnostic code: They’ll connect an OBD-II scanner and read the problem codes associated with different transmission parts.
- Check for common symptoms: Gear issues and transmission fluid leaks are telltale signs of a faulty solenoid.
- Test the solenoids: They’ll use a multimeter to test the electrical resistance of each solenoid coil (around 10 ohms, depending on the solenoid coil). They might also apply air pressure to determine if the solenoid valve opens and closes properly.
Once they’ve diagnosed the faulty transmission solenoid, they’ll replace it:
Step 1. Disconnect the Car Battery
The mechanic will remove the negative and positive battery terminals, respectively. They’ll also remove the dipstick from the transaxle to access the solenoid easily.
Step 2. Loosen the Fill Plug
Before draining the transmission fluid, they’ll loosen the fill plug to prevent it from getting stuck. This makes it easier to refill the pan later.
Step 3. Remove the Fluid Compartment
The mechanic will unscrew each bolt that secures the fluid compartment to the bottom of the transmission and remove the gasket from the transmission pan.
Step 4. Drain the Transmission Pan
Before draining the pan, they’ll place a container underneath the transmission to catch the fluid and remove the drain plug.
Step 5. Unscrew Fix Plate Bolts
They’ll locate the solenoid, disconnect all wires from the unit, and remove it from the fixing plate (the mounting surface where the solenoid is attached).
Step 6. Replace the Valve Body and Solenoid
The mechanic will turn the locking ring to release the fill plug from the valve. Afterward, they’ll remove the sleeve and each bolt attaching the valve body to the transmission.
They’ll pull the wires and pry the solenoid from the housing mount, replacing it with a new one.
Step 7. Reassemble the Components and Add Fluid
They’ll refill the transmission fluid and reattach all other components.
Now that you know about transmission solenoid replacement, read on to discover the costs.
How Much Does a Transmission Solenoid Replacement Cost?
You’ll pay around $250 to replace a transmission solenoid (including labor). If you need to replace a solenoid pack, the cost could reach $600.
The cost depends on your vehicle’s make and model, as well as the mechanic’s labor rate. For instance, a solenoid pack on a BMW will be more expensive than on a Honda Motor Company vehicle. Additionally, the complexity of the transmission system may lengthen the labor time.
Let’s clear up any other questions about transmission problems.
3 FAQs on Transmission Solenoid
Here are all the other essential solenoid details you should know:
1. What Are the Causes of a Faulty Transmission Solenoid?
There are two reasons why transmission solenoid fails:
- Electrical issues: Incorrect voltage (from electrical surges) can damage the solenoid coils and other components, such as the transmission control unit.
- Dirty transmission fluid: Over time, debris buildup in the transmission fluid can block the solenoid’s moving parts, specifically the valves, plungers, and springs.
2. Can You Drive with a Faulty Transmission Solenoid?
You shouldn’t drive with a faulty solenoid as it is dangerous and can cause additional transmission problems.
Gear issues (like getting stuck in a single gear) limit your control of the vehicle. Additionally, extended driving in “limp mode” (specifically at high speeds) causes the transmission to overheat, damaging other parts.
3. How Do You Maintain a Transmission Solenoid?
There are several things you can do to extend the lifespan of your transmission solenoids:
- Change the transmission fluid: Replacing dirty transmission fluid every two years prevents debris from clogging the fluid filter, valves, and other moving parts.
- Service your transmission: A transmission service every 30,000 miles prevents faulty components (like a clogged fluid filter) from causing a bigger transmission problem.
- Use synthetic transmission fluid: This fluid is more heat resistant, which prevents it from burning (burnt transmission fluid provides less lubrication).
- Use a secondary cooler: A secondary transmission cooler prevents your vehicle’s transmission from overheating in hotter climates.
- Avoid aggressive driving: Certain driving practices like hard stopping and over-revving strain your vehicle’s transmission, increasing the need for auto repair. Shift gears carefully, reduce speed over a longer period of time, and avoid over-revving.
Get Your Transmission Solenoid Fixed at AutoNation Mobile Service
Transmission solenoids are essential for proper lubrication and operation of the transmission system. If a solenoid breaks, you’ll experience gear issues that limit your control over your vehicle, putting you in danger.
Worried about getting to the mechanic safely?
AutoNation Mobile Service mechanics will replace your transmission solenoid in your driveway.
We offer easy online bookings and a 12-month | 12-000 mile warranty on all repairs and work on both automatic and manual transmission vehicles.
Contact us for a transmission service, solenoid repair, or any other auto repair assistance.