Automatic Transmission Solenoid Buyer's Guide
- The automatic transmission solenoid or simply transmission solenoid is a small electric device that’s commonly found in automatic transmission vehicles.
- The transmission solenoid is an electro-hydraulic valve found inside the transmission, which opens or closes the valve body’s channel.
- Inside the solenoid are a spring-driven plunger and a coil of wire that receives electric charge from the transmission control module.
- Solenoids are found inside the valve body of the transmission assembly, specifically inserted in the valve body channel, which is usually at the bottom part.
- There’s a wide range of transmission solenoid types based on two aspects: design and function.
- Bad transmission solenoids won’t usually cause an alarm. In fact, you may still drive your car not knowing that the transmission solenoid is already in bad shape.
- OE automatic transmission solenoids on CarParts.com may cost you $3 to $365.
Your car’s transmission system contains a lot of subcomponents, which almost all of them are moving. Each part has its own unique function to perform for the whole system to properly work. One component that’s so tiny you may have never heard before is the transmission solenoid.
Like all other solenoids, the transmission solenoid can fail and cause the entire transmission to go bad. In this article, you’ll understand the important details about this tiny transmission component, what could go wrong, and how much it costs to replace one.
What is an Automatic Transmission Solenoid?
The automatic transmission solenoid or simply transmission solenoid is a small electric device that’s commonly found in automatic transmission vehicles. You can think of it as the clutch of a manual transmission but in an automatic transmission setup. Inside is a cylinder-shaped coil of electromagnetic wire where electricity travels through.
What Does an Automatic Transmission Solenoid Do?
The transmission solenoid is an electro-hydraulic valve found inside the transmission, which opens or closes the valve body’s channel. It does this to control the flow of automatic transmission fluid, in relation to electrical impulses coming from engine speed sensors or the transmission control module.
Inside the solenoid are a spring-driven plunger and a coil of wire that receives electric charge from the transmission control module. This charge forces the plunger to open to let the transmission fluid to flow into the valve body. This, in turn, raises the pressure that’s needed to operate the clutches and bands.
The transmission solenoid word alongside engine sensors in changing gear speeds. The sensors are responsible for determining the perfect or ideal time for which the gears need to be changed. The transmission solenoid, on the other hand, relies on this information when changing gear.
Where to Find the Automatic Transmission Solenoid
Solenoids are found inside the valve body of the transmission assembly, specifically inserted in the valve body channel, which is usually at the bottom part. It is held in place by a bolt or a clamping plate at one side, while the other side is connected to the transmission control module via a wiring plug. Speaking of the wiring plug, most transmission solenoids are known to fail due to a damaged plug or wiring tail.
Another location for transmission solenoids is found on the side of the transmission assembly in some cars instead of being at the bottom. This is due to some layouts where the valve body and the pan cover is located on the side of the gearbox. The solenoid, being relocated on the side, links the transmission hydraulic system to the electrical system.
Types of Automatic Transmission Solenoid
There’s a wide range of transmission solenoid types based on two aspects: design and function. Here’s a breakdown of the different types of solenoid you’ll see in the market today:
Based on Design:
Because of their ability to open and close due to the kind of mechanism it has, this type of solenoid is named as the on-off solenoid. Inside an on-off solenoid, there’s a coil with a copper winding that’s meant to push the valve body’s plunger rod and open or close the channels to regulate oil transfer. A spring pushes the rod to its neutral position when an electric current is not present.
This type of valve first appeared in the early 2000s and was widely used in European and other expensive American cars. Solenoid-electric valves feature a more complicated construction compared to solenoids that feature a simple plunger and copper-wound coil. What’s good about this type of transmission solenoid is that it features a metal ball valve and has an oil channel with two outputs.
The solenoid-electric valve acts as a hydraulic valve, from which it earned the alternate name “solenoid-controlled valve”.
After the ‘80s, a new type of solenoid emerged in the automotive industry. It’s called the 3-way solenoid as it connects 3 channels and operates as shifters. These channels are opened and closed depending on the position in which the solenoid operates. In the “On” position, the metal ball opens channels 1 and 2 while, in the “Off” position, channels 2 and 3 are opened.
Designed for hydraulic control, this type of transmission solenoid operates in a different principle, similar to “valve/faucet”. Unlike the 3-way and other on-off solenoids, which are switchers, solenoid regulators like the power-width modulation, variable bleed solenoid, and variable force solenoid can open and close channels half-way rather than full. Solenoid regulators also feature complex designs and are considered rare.
Linear solenoids are widely used in Toyota, Volkswagen, and Volvo vehicles mainly because one of its largest manufacturers is Aisin, which happens to be the main supplier of the three said car manufacturers. This type of solenoid features a valve plunger that moves on the port-holed coupling clutch.
The new feature solved a common problem in previous designs, where the coupling clutch is found inside the valve body. Now, there’s no need to replace the valve body if the solenoid ever goes bad.
Based on Function:
Pressure Control Solenoid
Pressure control solenoids are used for closely monitoring the line pressure. It distributes oil to the solenoids and channels. It is considered as the pioneering solenoid-operated valve to have ever existed inside the valve body.
Torque Converter Clutch Solenoid
As its name suggests, this type of solenoid controls the torque converter lock-up by forcing the torque converter clutch into connected or blocked. It does this to improve efficiency and, in other cars, allow for true “sport mode” launch. It also receives the dirty and hot oil from the torque converter.
Shift solenoid is a simple shifter type of solenoid for shifting gears.
Signs you Have a Bad Transmission Solenoid
Bad transmission solenoids won’t usually cause an alarm. In fact, you may still drive your car not knowing that the transmission solenoid is already in bad shape. But in some cases, you may experience mild or noticeable changes in your ride. Good news, though, because fixing the transmission solenoid problem should be fairly easy if you bring your car to the mechanic before any bigger problems arise.
Here are some signs that your automatic transmission solenoid is badly needing a replacement:
- Delayed shifting when accelerating and decelerating
- Transmission may get stuck in neutral
- Rough or problematic shifting
- Loud revs even when the brakes are already engaged
- Transmission may fail to downshift or, in some cases, the engine can get super loud
How Much are OE Transmission Solenoid Replacements?
OE automatic transmission solenoids on CarParts.com may cost you $3 to $365 depending on the package or kit it comes with. That means you can buy a replacement for your car individually, in sets, or as part of a kit that includes other components. Find the perfect transmission solenoid for your car by indicating its year, make, and model in the filter tab under the search bar.