5 Transmission solenoid function

Your car has a transmission solenoid. When the ignition is turned on, it opens and closes. When you press the pedal, it goes in and out.

 

Your car is using the transmission solenoid to change the gear ratio at the moment of acceleration. So, what kind of function does your car have?

 

For example, if you press down on the pedal and turn off your engine, what happens then?

 

It’s probably not useful to think in terms of gears and ratios. It’s also unlikely that we can answer such questions so simply. We need a more sophisticated approach – one which starts with a good understanding of how transmissions work and goes from there.

 

There are two important things that come into play here: how it works (and how it doesn’t) and why you would want to know about it at all. The first involves a good understanding of how something works in general terms; we need to know what kind of thing it is (i.e., what kind of input/output mechanism) and why that might be useful for us (i.e., what benefit it gives us). 

 

The second involves understanding more specifically why this particular mechanism might be useful for us – i.e., what benefit or advantage our use of this mechanism provides – which is best left for another blog post!

 

Solenoid Function in Automatic Transmission

Synchronizing motor to transmission is one of the core tasks of an automatic transmission. The function of the solenoid transmission is to provide this synchronization, and should work as follows:

 

1. When the clutch pedal goes down, a solenoid connected to the rear-wheel drive shaft senses the pressure on the clutch pedal and travels back to a solenoid adjacent to the front-wheel drive shaft.
   
   
2. When the hand brake pedal is pressed, another solenoid goes back to the clutch shaft.
   
   
3. When both pedals are pressed together, they charge through a variable capacitor between two terminals that are coupled to each other by a wire (a "transmission" circuit). The current from these connections flows through a resistor which changes in value with road speed or load conditions, or with accelerator pressure applied at any point during driving — depending on which direction you want to go.
   
   
4. The voltage across this resistor varies with speed or load, causing it to discharge — thus changing its resistance — as you accelerate or decelerate (depending on which way you want to go). As long as you press down on either brake pedal at any point during driving, all three solenoids will continue firing; but if you release them before pressing down on either brake pedal again, they will stop firing — thus preventing slip when accelerating or decelerating — until you release both brakes again.
   
   
5. This process continues until only one solenoid fires; then it presents no more resistance and so allows charge through it quickly enough that another solenoid can fire quickly enough so that another circuit can be completed (and so on).