The transmission solenoid is responsible for opening and closing the valves that allow the transmission fluid to enter and do its job. If the solenoid is not working correctly, you will not be getting the right amount of fluid pressure that allows for the changing of gears. If you are experiencing trouble or difficulty when changing gears, you might have one of several issues involving the transmission solenoid. Here are some of the more common problems with a solenoid.
Plungers are stuck
The plungers in the solenoid are typically responsible in helping with the opening and closing of the valves. These plungers can become stuck either in or out meaning that the valves will not open or close as they should. This can happen when you have dirty transmission fluid or corrosion. You can easily fix this by removing the plunger with the aid of some WD40 and then cleaning the plunger bore.
Sticky transmission valves
In this case, “sticky” means exactly what it sounds like: the valves of the transmission have parts that are not working because they are stuck or are stuck as they try to do their jobs. Poor cooling generally causes this. When the transmission is operating under extreme heat, the valve bodies will tend to deteriorate much faster than you would expect. Carbon deposits can also account for sticky valves.
The wires inside the solenoid can break as a result of too much vibration or a sudden increase, or spike, in voltage. You can test this with a handheld ohm meter. A working solenoid will typically read between twenty and thirty ohms; if you do not get a reading, you will know that the wire is broken.
If the solenoid is working under extremely high temperatures or it experiences a spike in voltage, the plastic covering around the wire in the solenoid can melt, exposing the wire to other segments of the wire. When this happens, the solenoid will experience an electrical short. You can test this with a handheld ohmmeter; if the reading is below twenty ohms, you can assume that the solenoid has experienced a short.
Broken or weakened spring
Broken or weakened springs in the solenoid can cause high or low line pressure. Once the spring breaks or weakens and is unable to operate fully, the solenoid will need to be replaced. This can be a little pricy, but it is a necessary evil.
When you are dealing with transmission issues, you will want to check into all of the little things before you go head long into full on repairs or replacements. If you have experienced any of the traditional transmission symptoms, be sure to first check that the transmission solenoid is operating as it should. Of course, if the solenoid is operating correctly, you will have to move onto the next step; however, if the solenoid is the only part causing problems, you will save yourself the greater repair or replacement cost or the whole transmission.