How Does an Automatic Transmission Work?

Sun Auto Service Expert, published on 08/13/2015

If you’re like most, understanding the intricacies of your automobile is just like comprehending advanced nuclear physics. Yet that’s exactly how vehicle manufacturers want it to be. They design your car, truck, or SUV to work optimally on its own. Thus, if it’s working right, you won’t even notice what’s going on.

That being said, it is useful to understand exactly how the various systems and components of your vehicle work in order to better appreciate the need for regularly scheduled maintenance. Perhaps no other system is more important to comprehend than the one that gets and keeps your vehicle going: Your transmission.

Your Engine vs. Your Transmission

Wait a minute: doesn’t a vehicle’s engine provide its power? Yes is does, but something has to be able to disperse that energy to the wheels and control your vehicle’s driving dynamics, including speed, fuel consumption, and RPMs. That’s the job of your transmission. As your engine generates torque (the force that generates rotation), your transmission uses different gear ratios that regulate the rotational energy in order to spin the wheels. When engaging gears (or when you’re stopped), there needs to be some sort of mechanism that disconnects the transmission from the engine so that the engine can continue to spin. Otherwise, your engine would either die every time you stopped your vehicle, or you would be unable to control your acceleration. 

In a manual transmission, this is achieved by you engaging the clutch with every gear change. With an automatic, the gear change is triggered for you. The operating ease of automatic transmissions makes them a much more attractive option for drivers. Indeed, only about 10 percent of the vehicles in the American auto market still offer manual transmission options.

Understanding an Automatic

It’s important for you to ask yourself “how does an automatic transmission work?” simply because the majority of vehicles have automatic transmissions. Rather than utilizing a clutch, an automatic transmission uses a torque converter. This is a fluid coupling which utilizes a separate pump and turbine spinning in opposite directions within the converter itself, allowing the engine to spin independently of the transmission.

Rather than using different sets of gears to lock and unlock the transmission output shafts, an automatic transmission uses a single gearset to achieve the different gearset ratios. A complex hydraulic system regulates the various bands and clutches that control the gearset, and a gear pump pushes the transmission fluid through. A governor then regulates the movement of shift valves that supply the hydraulic fluids to engage the different gears. As fluid pressure within the governor increases or decreases, it forces the shift valves to close and open the different gear circuits. 

Understanding how your vehicle works is an important component to maintaining it. Yet, simply comprehending the complexities of your transmission may not equate to knowing how to correctly service it. When transmission problems arise, it’s better to leave the repairs to our team of ASE certified professionals here at Sun Auto Service. Together, we can keep your car running right.