Automatic Transmission Diagram: Parts And How They Work   

by Conner Mckay

I bet you’re familiar with the terms automatic and manual as it concerns cars. There’s a component in vehicles that transmit power from the engine to the wheels called transmission. It works automatically or manually and an automatic transmission diagram might be handy.

The automatic transmission diagram shows the parts of the transmission system, the connection between the torque converter, clutches, planetary gears, etc. You can get a more straightforward representation of the automatic transmission in a block diagram or 2D model.

The automatic transmission is a complex device made up of different parts working together to move the power generated by the engine to the car wheels. The mechanism involved in this movement classifies the car as automatic or manual. If you drive a modern vehicle, there’s a high chance it has an automatic transmission. Read on to learn about the transmission parts and what they do.

Parts Of A Transmission

The car transmission system comprises several parts; the planetary gear set, the torque converter, etc. with different functionalities and a common goal. The transmission system moves the power generated by the engine to the wheels and keeps the speed levels within the optimal speed range per minute (RPM).

Automatic Transmission Diagram

The transmission system is confusing, especially when you have to repair one of the parts. If one part of this component goes wrong, your car will malfunction. There are different types of transmission systems, and some of their parts differ too. We’ll cover the five main components of the transmission system.

Automatic Transmission Diagram #1 – Torque Converter

The torque converter is a mechanical device located between the engine and transmission. A fluid coupling allows the engine to turn at a different speed than the transmission while still providing power to the wheels. The function of the torque converter is to increase engine torque at low speeds and provide an automatic locking device for high-speed operation.

Automatic Transmission Diagram #2 – Planetary Gear Sets

The planetary gearset is located between the engine and wheels, allowing the car to move at different speeds depending on the driver’s requirements. We call it an epicyclic gearing system because it uses one or more sun gears and one or more planet gears connected by outside rings or carriers (called planet carriers).

The planet carrier is part of an outer ring gear, which also has internal teeth that mesh with the sun gear and planet carrier. The outer ring gear rotates around its axis while simultaneously rotating all other components on their axis. A clutch pack is also attached to the planet gears. The solar gear is linked to a drum, which is connected to one part of the clutch pack.

Transmission clutch packs are made up of several disks, half of which have splines on the outer edge and the other half on the inner edge. These alternate disks are designed to lock and revolve with one another. Planetary gears are found in manual transmissions.

Automatic Transmission Diagram #3 – Computer

The computer in your transmission monitors different sensors and performs many functions. It regulates the speed of your engine, making sure it doesn’t run too fast or too slow. It also controls the amount of torque going to the wheels.

Automatic Transmission Diagram

The computer ensures that all the systems are working well together. For example, if you press on the accelerator pedal, it will send a signal to the engine so that it can speed up.

Automatic Transmission Diagram #4 – Hydraulic System

The hydraulic system in your transmission consists of a reservoir, pump, valve(s), and actuator(s) that work together to deliver power to the wheels. The hydraulic system uses fluid pressure to provide smooth shifting and reliable transmission. The oil pump moves the oil around the system.

It is driven by either a belt or chain from the engine’s crankshaft, depending on whether it’s an automatic or manual transmission. The hydraulic fluid flows from the reservoir into an actuator valve located inside each gear in the transmission.

Inside this valve is an electromagnetic solenoid that opens or closes based on how much pressure your foot applies to the gas pedal. When you press down on your gas pedal, it opens up this valve and sends more fluid into each gear. The pump supplies pressurized fluid to all transmission parts, including the gearbox and clutch assembly.

Automatic Transmission Diagram #5 – Transmission Casing

The transmission casing is the outer housing of the transmission. It is made up of steel or aluminum and encloses all moving parts inside. The primary purpose of the casing is to protect the gears, bearings, and synchronizers from dust, water, and other particles that might damage them.

The transmission casing also helps to dissipate heat from inside the transmission by allowing air to flow through it. This cooling effect keeps temperatures down in hot climates, which reduces wear on components.

Automatic Transmission Diagram #6 – Brake Band

The transmission brake band is a metal strap that wraps around the inside of the transmission. It is attached to the engine’s crankshaft and is used to engage and disengage the clutch. When engaged, the brake band applies pressure against a spring-loaded clutch release lever, allowing the transmission to shift gears. When not engaged, the clutch is free to move from forward to reverse as needed by pressing on it with your foot pedal.

Different Types Of Transmissions

There are different types of transmissions in vehicles. The popular ones are manual, automatic, and CVT transmissions. If you’re not sure what type your car has, contact a technician to look at your setup to understand the type of gearbox your vehicle has.

1. Automatic Transmission

The automatic transmission system consists of 3 main parts, the torque converter, planetary gears, and clutches. The torque converter is connected to the engine, the gear system, and the transmission. The flywheel part of the torque converter pushes out fluid as it rotates. This hydraulic fluid causes the turbine to spin.

The fluid circulates independently in the two sections and through the stator. If you drive an automatic transmission vehicle, you do not need to change the forward gears. The automatic transmission system is quite convenient. It makes driving easier, but it’s expensive to maintain. Also, it houses so many parts, and failure of any can be fatal.

2. Automated Manual Transmission

The automated manual transmission, also called Direct Shift Gearbox (DSG ) or a Sequential Manual Gearbox (SMG), is a manual and automatic transmission. The AMT uses an accelerator and brake pedal in place of clutch and shift gears. To change gears, you won’t need the clutch pedal. When you press on the accelerator pedal, the engine sends power through a gearbox to drive the wheels.

You can also shift gears manually by pressing buttons mounted on the steering wheel or dashboard. These buttons control how much torque goes to each wheel, giving you more control over your vehicle’s performance during acceleration, braking, and cornering situations.

In the AMT, a hydraulic system connects to the car’s Electronic Control Unit (ECU). It has preset RPM settings from the ECU. The system calculates the PMs and sends the input to the ECU, sending signals to the actuators that operate the clutch and gearbox. It allows for automatic or manual forward gear shifts through the gear selection or buttons or paddles on the steering wheel.

The AMT is more convenient than the manual transmission. But it doesn’t eliminate the manual components; you can choose to use the manual mode. It saves fuel. The issue we have with the AMT system is the preset RPM levels; you can’t always overtake or go beyond the speed regardless of the circumstances.

3. Manual Transmission

If you drive a manual car, you’ll have to change the gears using the moveable gear selector and the clutch. The manual transmission in cars is the most common type of gearbox. Manual transmission, or ‘stick shift’ as it’s often called, is a mechanical gearbox that uses synchromesh (synchronized) gears.

The driver uses their feet to change gears by depressing pedal(s), which actuate a lever connected to the gear lever and release fork. The clutch must be depressed before changing gear and released afterward. It consists of three main parts: a gearbox, clutch, and driveshaft. The gearbox contains the gears that transmit power from the engine to the wheels.

The clutch allows you to disengage the engine from the wheels when you stop at a traffic light or are about to make a turn or change lanes on a highway. And finally, the drive shaft connects both components and transfers power from the engine to all four wheels (or just two wheels if your car has front-wheel drive).

These days, most new cars come with automatic transmissions instead of manuals. But if you’re looking for an older car or something with more character than a modern vehicle, you may run across one with this type of transmission. Manual cars are harder to drive, but they’re perfect for off-roading.

4. Intelligent Manual Transmission

Intelligent Manual Transmission (IMT) is a clutchless manual transmission system that uses brakes and an accelerator pedal. The Intelligent Manual Transmission (IMT) is designed to give drivers an experience similar to that of an automatic transmission but with the added benefit of improved control over their vehicle.

It has been designed as a replacement for traditional manual transmissions so that drivers can enjoy all of the benefits associated with automatic transmissions without changing their driving style or getting used to using a new kind of gearbox.

In an IMT, the driver still has to select gears manually, but there are no traditional clutches or shifters. Instead, the TCU controls these functions. This design allows for smoother shifts and better fuel economy. IMT vehicles give you an advantage in gear selection. It’s different from the automated manual transmission.

5. Continuously Variable Transmission

Continuously Variable Transmission (CVT) is a type of transmission that can vary its drive ratio infinitely, unlike other transmissions with a fixed number of gear ratios. In its simplest form, a CVT has two spur gears of different sizes attached to the same shaft but not mechanically fixed to each other.

The CVT gearbox consists of two pulleys: a large one connected to the engine and a smaller one connected to the wheels via belts. The idea is that the pulley wheels turn at different speeds depending on how fast you drive. When you accelerate or decelerate, they change their diameter accordingly, changing gear ratio and allowing you to keep your revs low while still maintaining speed.

In most cars with CVTs, two sets of pulleys and belts work together to achieve this effect. CVTs are used in many automobiles because they’re better for fuel efficiency than other transmissions, such as manual and automatic transmissions.

6. Semi-Automatic Transmission

A semi-automatic transmission is a manual transmission that allows for driver control and shifting but doesn’t have a clutch pedal as the manual transmission does. The car’s CPU and sensors operate the clutch while the gear ratios control the speed of the wheels. This type of transmission is often found in Hyundai cars.

They are not fully automatic because they require the driver to shift gears manually. However, they offer many of the same advantages as fully automatic transmissions, including improved fuel economy and reduced emissions. Semi-automatic cars are easy to drive but expensive to maintain.

7. Dual-Clutch Transmission

A dual-clutch transmission uses two separate clutches for odd and even gear sets. It can fundamentally be described as two individual manual transmissions (with their respective clutches, gear sets, and hydraulic systems) within one housing and working as one unit. A DCT is typically built for optimal efficiency and a more spirited driving experience than a conventional automatic transmission.

DCTs are more expensive than traditional automatics because they require more complex components and computer controls. They also require more maintenance and adjustment than standard transmissions because they have more complex parts.

8. Sequential Transmission

Sequential transmission is a non-synchronous manual transmission with a gearbox that allows the driver to change gears sequentially instead of simultaneously. Each gear is selected by moving the shift lever and then releasing it to lock it into place. What makes sequential transmissions special is that instead of having separate gears, they have only one gear that moves sequentially like a bicycle chain.

This allows for more precise gear selection and a smoother and quicker shift. Sequential transmissions have become popular in racing because they make it easier for drivers to shift gears when driving at high speed quickly. They also help improve fuel economy by eliminating unnecessary shifts found in a traditional shift pattern with a manual transmission.

9. Torque Converter Transmission

Torque Converter Transmission (TCT) is a transmission that uses a fluid coupling to transmit power from the engine to the wheels. The torque converter is located between the engine and transmission. It functions as a clutch that is engaged when you start the car. TCTs are used in most modern cars and light trucks, and some heavy equipment. They do not require external shifting of gears but rather use planetary gear sets to provide an infinite number of gear ratios.

10. Tiptronic Transmission

A Tiptronic transmission is a variation of the automatic transmission that can be operated by the driver using a console-mounted shift lever in manual mode. In addition, it can be shifted automatically by computer control in response to engine speed and throttle position. It functions similarly to a manual transmission but without the clutch. This gives you more control over the gears.

7. How A Torque Converter Works

The torque converter works has three parts, the impeller, turbine, and stator immersed in hydraulic fluid. The impeller rotates and generates a centrifugal force that spins the turbine as the engine moves. The turbine blades rotate and move the transmission system, driving the vehicle. The turbine stops spinning when you turn off the engine, but the impeller keeps rotating.


The impeller is connected to the housing joined to the engine shaft. The impeller blades rotate when you turn on the engine, generating a centrifugal force. These blades direct the centrifugal force to the turbine.


The stator is between the impeller and the turbine. It directs the fluid from the turbine to the impeller. It only rotates in one direction because it’s attached to a one-way clutch—the stator multiples torque by changing the direction of the transmission fluid coming from the turbine.


As the force hits the turbine, its blades rotate opposite. The turbine is connected to the transmission’s input shaft on the engine side. The transmission’s input shaft moves and sets your car in motion as the turbine blades spin.

Automatic Transmission Diagram

Facts about Automatic Transmission Parts and Functions:

  1. An automatic transmission is complex and uses fluid, gears, pumps, and much more to transmit power from the engine to the car’s wheels.
  2. A transmission is needed to keep the engine running when the wheels are stationary and to control and carefully apply the engine’s power output when the car must accelerate.
  3. The gears in an automatic transmission are there to multiply or divide the torque, making it possible to drive at different speeds with the same engine speed.
  4. The torque converter is an art in itself and consists of four parts: impeller, turbine, stator, and lock-up clutch.
  5. The impeller is connected to the crankshaft via the flywheel and rotates at the same speed as the crankshaft, propelling the automatic transmission fluid to transfer energy to the turbine.
  6. The turbine receives the fluid pumped by the impeller and connects directly to the transmission’s input shaft, and its speed affects and is affected by the wheel speed, making it possible to keep the engine going even when the wheels are stationary.
  7. The stator lies in between the turbine and the impeller and turbine, is responsible for torque converting, and sends the transmission fluid back to the turbine, making it somewhat of a closed-loop system.
  8. The lock-up clutch engages and locks the turbine with the impeller, mitigating any loss of energy that would otherwise be present.
  9. An automatic transmission uses planetary gears consisting of a sun gear, planet gear, and ring gear to enable different amounts of torque to be delivered to the wheels.
  10. Brake bands and clutches are important parts of an automatic transmission that work in different ways but are both needed to engage or disengage a gear properly, and the output shaft is what makes the car move.

Frequently Asked Questions On Automatic Transmission Diagram

Here are some popular FAQs:

What Is A Transmission

The transmission can be described as a system of mechanical components that provides different mechanisms to convert the power produced by an engine into mechanical energy at the output shafts. The transmission delivers the power generated by the engine to the wheels. Transmissions are designed to allow the input shaft to rotate at an angle to that of the output shaft. This is usually achieved with one or more sets of gears; these sets can be called “gear stages” or “gear steps.” The gears ensure that the engine and the wheels run at different speeds at all times. It uses the gear ratios to achieve this. When you shift up a gear, you’re changing the ratio between how fast your engine turns and your wheels turn. Your car starts off with a low gear ratio; when you change the gears, the gear ratio changes, and the car speeds up.

What Does The S Mean On A Gear Shift

The S on the gear shift stands for sport mode. The sport setting is an RPM feature on some automatic transmission cars. Using it increases the vehicle’s RPM but maintains a lower gear ratio. The car will move faster because the increased RPM gives you a sporty feel as you drive. The downside of using sports mode increases fuel consumption and risks transmission. At accelerated speed, the fuel injectors send more fuel into the cylinder. You shouldn’t use the sports mode except when necessary.

Do Automatic Cars Have A Clutch

Automatic cars have a clutch but not a clutch pedal. Automatic transmissions use a set of hydraulically operated clutches to control their gears. The clutch doesn’t need to be depressed because there is no mechanical connection between the engine and transmission. When you push on the accelerator pedal, the engine turns over and moves the car forward.

How Does An Automatic Transmission Work

The automatic transmission in vehicles uses a hydraulic system to shift gears in your car. To understand how the automatic transmission works, you need to know the parts involved and their functions. The torque converter is a mechanical device used in automatic transmissions. A fluid coupling allows the engine to turn the transmission’s input shaft by using energy stored in its rotating elements. The hydraulic pump is connected to the transmission’s torque converter, which powers the internal workings of your automatic transmission. The crankshaft of your engine drives the hydraulic pump. The primary purpose of the planetary gears is to deliver power smoothly from one gear ratio into another without causing any jerking movement as it happens. It engages with the teeth on the ring gear, which is mounted to the engine flywheel.

When Did Automatic Transmissions Come Out

Automatic transmissions came out in 1921 when a steam engineer, Alfred Horner Munro, invented them. The design was patented in 1923. The first commercially available automatic transmission was developed by General Motors and introduced in 1939 in Oldsmobile’s 60 Series cars.

Is The Transmission Part Of The Engine

The transmission is not a part of the engine. It only moves power from the engine to the car wheels, but it is a separate unit. Manual transmissions require the driver to shift gears manually by moving the shifter up or down, while automatic transmissions make the shifting process easier by shifting gears automatically.

What Kind Of Transmission Do I Have

Check the white sticker on your car door to confirm what type of transmission your car is operating. This paper contains specific details about the vehicle. Check for the letters TR; underneath it is a number code. Contact an automobile dealer to enquire what type of car transmission has that code.

Conclusion On Automatic Transmission Diagram

Transmission is a vital component in vehicles. A fault in the transmission system affects the gears and can be dangerous. The automatic transmission system is convenient, but it consists of many parts, making it complex.

However, the automatic transmission diagram identifies all the planetary gears, torque converter, and other essential parts. If you ever wondered what the transmission system looks like, you know all about it now.

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