In an ordinary automatic transmission, the gears are shifted by directing the pressurized transmission fluid to a variety of hydraulic clutches. On older designs, the fluid is directed by valves through the ports of the valve body, which react to different torque and speed and position-related mechanical inputs.
On newer designs, the fluid is directed through a simpler valve body by electric solenoids, which are operated by either the PCM or the TCM. On most applications, each solenoid operating circuit has built-in self-diagnostics.
So, if a solenoid is not operating as designed, an engine light is triggered.
Costs of Transmission Solenoid Replacement
Some estimates of the solenoid replacement cost using a labor rate of $100 per hour are illustrated below:
- For a 2013 Honda Accord with a 3.5-liter engine
The labor time to replace a shift solenoid is about an hour. There is a solenoid assembly on the valve body, as well as a separate “C” solenoid; all mounted on the top of the transmission housing.
A factory solenoid assembly costs about $614, and a “C” solenoid costs about $154. This makes the job about $714 to replace the solenoid assembly and about $254 to replace solenoid “C”.
- For a 2015 Dodge Dart with a 2.4-liter engine
The labor time to replace a transmission solenoid is 1.4 hours. On this vehicle, the shift solenoids come as a non-serviceable valve body assembly located inside the transmission pan. A factory valve body costs about $1,120. This makes the job cost around $1,280; adding in an average cost for the transmission fluid to be refilled.
- For a 2012 Chevrolet Silverado with a 5.3-liter engine
The labor time to replace a transmission solenoid is 3 hours. The shift solenoids are located on the valve body inside the transmission pan. Availability is limited, even through dealer sources. However, there is a PA Cargo solenoid body assembly available for about $237. The total cost to complete the job would be about $567, which includes the cost of fluid to refill the transmission.
- For a 2010 Hyundai Sonata with a 2.4-liter engine
The labor time to replace a transmission solenoid is about 3.7 hours. The solenoid assembly is located inside an upper fluid pan. There are five shift solenoids, and Standard replacements are about $71 each. This makes the replacement of shift solenoid cost about $461, including transmission fluid and gasket.
In most cases, replacing a transmission solenoid begins with an engine light, and follows specific diagnostic procedures to verify the problem. Usually, there would be a one-hour diagnostic charge on top of the replacement costs for the part
Transmission Solenoid Replacement
Usually, the procedure is relatively simple. There is a PCM or TCM driver that can be verified, and then, the wiring from the module to the transmission.
After that, there is only the wiring harness at the transmission itself, which can’t always be ruled out without some disassembly. Replacement of a transmission solenoid is sometimes easy. They can be located externally on the transmission housing.
Sometimes they are located on the valve body, which is usually right inside the transmission pan. On transmissions without a lower pan, sometimes, the solenoids are hidden under a pan on the side or top of the transmission.
Parts availability is mostly spotty. Some solenoids are replaceable separately but have no aftermarket sources. Some have aftermarket sources but aren’t available yet through manufacturers.
One practice vehicle manufacturers tend to do sometimes on newer vehicles is to not offer parts, only assemblies. So a solenoid failure, even if it can be diagnosed with some certainty, can still wind up being a replacement of a whole transmission.
The advantage to the manufacturer isn’t necessarily just selling a more expensive part (as in most cases, this will be done on vehicles under factory warranty), but they get the old transmission back and can analyze it for wear. This is useful in refining diagnostic procedures, as well as verifying wear characteristics which can lead to improved durability.
Any time the transmission has to be dealt with or opened up, that’s a good time to go ahead and do a transmission service, or at least a drain and fill. On some transmissions, that’s unavoidable if there is a lower transmission pan that has to be removed to access a solenoid on the valve body.
In that case, there is also usually a transmission filter, which would ordinarily be replaced, as it has to be removed anyway. On other transmissions, there is no pan, and a drain and fill is an additional step. As contaminants or debris in the fluid can contribute to solenoid failure, it’s not a bad idea to renew the fluid.
Sometimes, a problem that looks initially like a transmission solenoid can wind up being the wiring harness to the solenoids. If the solenoids and the wiring are external, then, it’s easier to diagnose.
However, if the solenoids and the wiring are internal, sometimes, disassembly is needed. In the case of the 2015 Dart, for instance, the wiring harness runs through the inside and the replacement requires removing the valve body. So, it’s about the same labor as a solenoid as the wiring harness itself costs about $380 through OE sources.