Automatic Transmission The Complete Guide to How It Works

The automatic transmissions you find in current cars today definitely make the most complicated mechanical piece inside your vehicle. They are so complicated because they contain many systems that work succinctly to keep your vehicle running properly. These systems include mechanical, hydraulic, electric, and computer controls. You can see why it takes a specially trained individual to service this one particular part.

When the automatic transmission is working as it should, you do not even notice it doing its job. However, when the automatic transmission fails in some way, it can cause serious issues with many symptoms. This article will give you an overall look into your automatic transmission so you can get a better idea of how this marvelous contraption functions.

How Does an Automatic Transmission Work?

An automatic transmission can be found underneath your vehicle attached to the back of the engine. It functions by taking power from the engine and supplying it to the drive wheels. The transmission is also responsible for keeping your RPMs within the ideal range to help your vehicle run at its peak. To do so, the automatic transmission utilizes various gear combinations.

  • For example, when your transmission functions in first gear, the engine is turning much faster than the wheels are.
  • When you are in a higher gear, the engine is relaxing even though your actual speed is much faster than at first gear.
  • Besides the forward gears, your automatic transmission also has a neutral position. This one disconnects the wheels, and of course, a reverse gear to allow you to go backwards.
  • Finally, there is also a park position where a latch apparatus, that is similar to a lock, inserts into an opening in the output shaft. This stops the drive wheels from having the ability to turn- locking them in place.

Types of Automatic Transmissions

The automatic transmission can be available in two basic types:

1. Rear Wheel Drive

If your vehicle is a rear wheel drive, the automatic transmission will usually be located under the bump of the center floor board, alongside your gas pedal, and mounted to the rear of your engine. A long drive shaft leads from the rear of the transmission to the back wheels of your vehicle. Here it connects to the final drive located within the rear axle. Here, power transfers to the back wheels.

You can follow the path that the power takes in a rear wheel drive vehicle very easily.

  1. It begins in the engine.
  2. Then it is transferred to the torque converter.
  3. After this, it is sent to the transmission, through the drive shaft to the final drive.
  4. Finally, it is divided between the back wheels.

2. Front Wheel Drive

If you own a front wheel drive vehicle, you will have something called a trans-axle. This is where the automatic transmission combines with the final drive. You can usually find the set-up mounted sideways on the side of the engine that faces towards the back of your car. You will notice the trans-axle directly connects to the front axes since the power is sent straight to the front wheels.

  1. The power travels similarly to the rear wheel drive by starting at the engine and then to the torque converter. However, in this type of transmission, the power is then sent through to the trans-axle by means of a 180 degree turn to get to the transmission.
  2. Then it is sent back up to the final drive and again, split between the two wheels, only this time it is the front wheels.

There are other arrangements where the mounting is in a different direction or area. However, these two basic set ups are most popular in modern vehicles.

Components in an Automatic Transmission

Automatic transmissions are home to many components in several systems that all come together to harmoniously work together. These are the major pieces you will find:

  • Planetary Gears: These gears provide the forward and reverse to your vehicle and is part of the mechanical system.
  • Hydraulic System: Thus system helps control the planetary gears through the use of pressurized fluid. The fluid is sent to the oil pump through the body valve. The planetary gears are then controlled by the clutches and bands in the valve body.
  • Seals and Gaskets: Usually non-asbestos, graphite or rubber o-rings or a shape customized to fit your application. These seal and fill gaps between tow surfaces that otherwise do not fit perfectly. Gaskets will prevent leakage of fluids.
  • Torque Converter: This component mimics the job of a clutch. It allows a vehicle to come to a complete stop while the engine is still running.
  • Governor and Modulator: Monitors speed and the throttle position. Some vehicles use a Throttle cable. This helps your vehicle recognize the proper time to shift gears.
  • Computer: More modern vehicles utilize the help of an on board computer system. It tells the solenoids where and when to direct the oil flow to a specific component.

Maintenance and Issue Identification

It is imperative to catch issues early on to avoid major damage and repair cost. Here are 3 things to keep an eye out for:

  1. Look for leakage onto the ground under your vehicle.
  2. Check the fluid to make sure it is a transparent red and not cloudy. Also, be sure it does not have a burnt odor to it.
  3. Be aware of new noises, vibrations, and odd or harsh shifting. Erratic shifting, whining, and other oddities should be checked on by a certified mechanic to avoid further damage.

Maintenance routines will help keep your transmission and all of its components in top performance condition and elongate its life.

  1. Check your owner’s manual for recommended interval transmission fluid changes. Typically it should be between 15 k to 100 k miles. Many experts recommend a change every 25 k.
  2. Be sure to use the correct type of fluid when adding to or changing. Using the wrong fluid can gum up the works and cause horrible damage.
  3. When in doubt, take it to a service center.

In the End

Your automatic transmission, in all rights, is a work of art. It brings many systems together harmoniously to get your vehicle running smoothly and in top condition. It is also very complex meaning that when there is an issue or a service is necessary, you should consult a skilled tech.

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