Mechanical Basics

What is an Automatic Transmission?

Automatic Transmission (or Automatic System) is the process of transferring the power (generated by the engine) from the Automobile Engine to the Gearbox automatically. It works without any human or manual efforts to change the gear or it is defined as automatic shifting of Gear Ratio according to the situation without any human interference. The Gears that play a prominent role in Automatic Transmission are Planetary Gears.

Automatic Transmission – Its Parts, Types Of Modes, Working, Automatic Transmission Cars, & AdvantagesAutomatic Transmission (AT) is also called as the Self-Shifting Transmission System. Generally, there are two types of transmissions; they are Manual and Automatic Transmissions. In Manual Transmission vehicles, the driver is supposed to change the gear according to the speed he moves but in an Automatic System, the process will be Automatic.


What can we learn from this post?

  • Automatic Transmission Gearbox
  • Automatic Transmission Parts
  • How Does Automatic Transmission Work?
  • Automatic Transmission Cars
  • Types of Modes in Automatic Transmission System
  • Advantages of Automatic Transmission
  • Conclusion

Automatic Transmission Gearbox:

The process of automation or automatic gearing is done by the special gears called Planetary Gear Train or Epicyclic Gears. It is the type of gear or gear trains that are responsible for the Automatic Transmission System in the vehicles. It can also be called as Automatic Transmitting Gears also.

Due to this planetary gear train (or automatic transmitting gears), the vehicles can automatically change the Gear Ratio according to the speed of the vehicle or the situation of the vehicle, so there is no necessity of external interference like human power to change the gears.

Automatic Transmission Parts:

As mentioned above, the typical AT Gearing System is because of Planetary Gear Train System; the planetary gear train system consists of a number of components, they are

What is an Automatic Transmission & How Does Automatic Transmission Work?

  1. Sun gear
  2. Planet gear
  3. Ring gear
  4. Carrier
  5. Clutches
  6. Bands

The Sun Gear, Planet Gear, and Ring gears are mounted one above the other; according to the actuation of the Friction Clutch, the gears will rotate and stop. By the rotation of gears, the transmission of energy from the Engine to the rear wheels can be achieved.

The construction of the Gears can be seen in the above image. The planetary gears are held by the Carrier and move at the same time with the same ratio.

How Does Automatic Transmission Work?

What is an Automatic Transmission & How Does Automatic Transmission Work?

Focusing on the working of planetary type of Gear Train, Automatic Transmission system consists of Torque Converter that acts like a Clutch; it will connect the Engine and the Planetary Transmission system or Planetary Gear Box. It will Engage and Disengage the input, output shafts according to the requirement. All bands and clutches will be actuated according to the speed of the vehicle that it wants to move.

The speed of the vehicle can be accelerated by the accelerator and the gearing ratio depends upon this Planetary Gear Train System, the reductions or overdrive ratios will be varied by this Gear Train. The Planet Gears will be attached by Carrier so all the three planet gears can rotate at a similar speed or ratio.

The process or the principle sequence of Engaging and Disengaging of Gears according to the speed is controlled by the Internal Programmed device called SPRAG, it is nothing but a Roller Clutch that can be used for routing up-shifts and downshifts.

The Roller Clutch will remove the sensitivity of the time while engaging and disengaging the Gears. The rotation of gears depends upon the speed where sometimes planetary gears will rotate idle, does nothing, and sometimes the Sun gear.

Automatic Transmission Cars:

All Luxury Cars are built with Automatic System but nowadays some of the Non-Luxury cars are also using this technology for a good performance so, some of the Luxury and Non-Luxury automatic System cars or vehicles are as follows:

Luxury Automatic Cars:

  • BMW Cars Mercedes
  • Audi.
  • Porsche, etc

Non-Luxury Automatic Cars:

  • Hyundai Creta
  • Toyota Fortuner.
  • Volkswagen Tiguan, etc.

We can find Heavy and Transporting Vehicles with AT, some of the models are

What is an Automatic Transmission & How Does Automatic Transmission Work?

  • The new Eicher Pro 3016.
  • The Mercedes Vehicles.
  • Tata Buses.

Types of Modes in Automatic Transmission System:

What is an Automatic Transmission & How Does Automatic Transmission Work?

The AT vehicles consist of few basic modes on their Gear Rod; they are Drive mode (D) to move the vehicle, Park Mode (P) to park the car steadily at parking, Sport Mode is to move the vehicle fast, Neutral Mode helps to stop and still the vehicle, Reverse Mode to move back.

Advantages of Automatic Transmission:

  • Reliable Performance:

The Automatic System is more reliable in performance and can easily be controllable at high speeds due to its technology.

  • Torque Multiplication.
  • Fuel Economy
  • Automatically Transmitting Cars or Vehicles do have a Smooth Drive.


The AT vehicles are more comfortable and easy to handle because there is no manual work of changing the gears. They are becoming more expandable in the market, and at the same time, they are more efficient in power transmission too. The evolution of modern technology is taking place.

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