What Is Automatic Transmission and How Does it Work?

What is Automatic Transmission?

Automatic transmission is a multi-speed transmission that is used in cars and does not require the driver’s input to change gears in normal driving conditions. The most common type of automatic transmission is the hydraulic transmission, which uses a planetary gearbox, a hydraulic control, and a torque converter.

Automatic transmissions are also known as self-shifting transmissions or AT or dual pedal technology because this system works without a clutch pedal. It is a type of car transmission that can automatically change the gear ratio as the vehicle moves, eliminating the need for manual gear shifting.

Automatic transmissions are particularly efficient in heavy city traffic, where drivers of vehicles equipped with manual transmissions must constantly shift gears.

Parts of Automatic Transmission

There are different parts of an Automatic Transmission:

  • Transmission Casing.
  • Torque Converter.
  • Pump (aka impeller).
  • Turbine.
  • Stator (aka Reactor).
  • Torque converter clutch.
  • Planetary Gears.
  • Brake Bands and Clutches.

1. Torque Converter

A torque converter is located between the engine and the transmission. It looks like a donut and sits in a large opening in the bell housing of the gearbox. In terms of torque transmission, it has two main functions.

  • It transfers power from the engine to the input shaft of the transmission
  • Multiplies output torque of the engine

It performs two functions thanks to the hydraulic force provided by the transmission fluid inside the gearbox.

2. Torque converter clutch

To prevent this energy loss, most modern torque converters install a torque converter clutch on the turbine. When the vehicle reaches a certain speed (typically 45 to 50 mph), the torque converter clutch engages and the turbine rotates at the same speed as the pump. When the converter clutch is engaged, the computer controls.

3. Planetary gear

An automatic transmission automatically increases or decreases the gear ratio. This is possible thanks to the innovative design of planetary gears.

A planetary gear consists of three components:

  • Sun gear. In the center is the planetary gear set.
  • Planet gears/pinions and their carriers. Three or four small gears surround the sun gear and are in constant mesh with it. A planet gear (or pinion) is mounted and supported by a carrier. Each of the planet gears rotates on its own separate axis which is connected to the carrier. The planet gear not only rotates, but also rotates around the sun gear.
  • The ring gears. A ring gear is an external gear and has internal teeth. The ring gear surrounds the rest of the gear set and its teeth are in constant mesh with the planet gears.

4. Brake Bands

The brake band is made of metal and coated with organic friction material. The brake band can be tightened to keep the ring or sun gear stationary, or loosened to allow them to rotate. The tightening or loosening of the brake band is controlled by a hydraulic system.

5. Oil pump

The pump is like a fan. It has a series of blades extending from the center. The pump is mounted directly on the torque converter housing and is bolted directly to the engine flywheel. As a result, the pump rotates at the same speed as the engine crankshaft. The pump “pumps” the transmission oil from the center to the outside.

How does an Automatic Transmission Work?

The most common type of automatic transmission uses hydraulic power to shift gears. This device combines a torque converter or fluid clutch with a gear set that provides the desired gear range for your vehicle. The torque converter connects the engine to the gearbox and transfers power to the gears with hydraulic fluid.

This device replaces the manual friction clutch and allows the car to standstill without stalling. When the engine transmits power to the torque converter pump, the pump converts this power into transmission oil that drives the torque converter turbine.

This device increases the force of the fluid and returns more force to the turbine, creating a vortex force rotation that turns the turbine and the attached central shaft. The force created by this rotation is transmitted from the shaft to the first planetary gear set of the transmission.

This type of transmission has something called hydraulic control. The transmission oil is pressurized by an oil pump and its speed can vary depending on the vehicle speed, tire revolutions per minute, etc.

The gear pump is located between the planetary gear assembly and the torque converter and draws transmission oil from the reservoir and pressurizes it. The pump inlet leads directly to the torque converter housing which is attached to the engine flex plate. If the engine is not running, the transmission will not have enough hydraulic pressure to work and the car will not start.

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A planetary gearbox is a mechanical system in which the gears are connected by a series of belts and clutches. When the driver shifts gears, the belt holds one gear in place while rotating the other, transferring torque from the engine to upshifts or downshifts.

Different gears are sometimes called sun gears, ring gears, and planet gears. The location of the gear determines how much power flows from one gear to the next and to the engine during the shift.

Gears of an Automatic Transmission

The gears in the automatic transmission are:

When shifting the vehicle into drive mode, engage all available forward gears. This means the transmission can move through the entire gear range as needed. Six-speed automatic transmissions are the most common number of gears, but older cars and entry-level compacts may still have four or five automatic transmissions.

3rd gear blocks. The transmission in 3rd gear or limits it to 1st, 2nd and 3rd gear ratios. It gives you the power and traction you need to move uphill, downhill, or tow your boat, RV, or trailer. Most cars automatically shift into 3rd gear when the engine reaches a certain RPM to prevent engine damage.

2nd gear blocks. The 2nd gear transmission or limits it to the 1st and 2nd gear ratio. This equipment is ideal for riding uphill and downhill in slippery conditions and riding in ice, snow and other inclement weather.

First gear. It is used when you want to lock the transmission in first gear. However, some vehicles automatically turn off this gear to protect the engine at certain speeds. Like 2nd and 3rd, this gear is great for towing, climbing hills, and driving in slippery and icy conditions.

What are the types of automatic transmission?

There are most commonly used gearboxes in this category include:

1. Automated Manual Transmission

An automatic manual transmission (AMT) or semi-automatic transmission is not basically an automatic or clutch less transmission, but rather a manual transmission that allows you to easily shift gears without stepping on the clutch.

The mechanism of this type of transmission involves the use of two key parts: a hydraulic actuator system and an electronic control unit that engages and disengages the clutch during gear changes. Essentially, it’s just a kit that can be added to a regular manual transmission, providing a cost-effective solution for automakers.

2. Continuously variable transmission (CVT),

The continuously variable transmission (CVT) is the most unique clutch less transmission compared to the other transmissions mentioned above. While other transmission units have a certain number of gears that must be shifted to maintain acceleration, CVT units do not. like these

The number of gears in a transmission system, also known as the speed, usually has a limited number of gear ratios assigned to each gear. So, you have to cross the point to go faster. CVTs, on the other hand, have special gears that are variable in all driving situations and can easily be changed through a continuous range of effective gear ratios.

This allows you to control engine speed or RPM to accelerate or decelerate based on throttle manipulation. CVT transmissions are also mainly used in two-wheeled vehicles, especially scooters where acceleration and braking are critical. Some cars are also equipped with pedal shifters for the convenience of the driver.

3. Double clutch transmission (DCT)

A dual-clutch transmission (DCT) works on the same principle as an AMT, but as the name suggests, a DCT uses two clutches instead of one. One for even and odd gears, more efficient than AMT.

Simply put, a DCT transmission is like two manual transmissions in one housing. Here’s how it works: the clutch is in odd gear while the computer calculates the next even gear needed. The second clutch is ready to engage the gear, just change the clutch at the right time.

Like all standard automatic transmissions, the DCT unit has a simple P, R, N, D gear selector and no clutch pedal. It can be changed independently or controlled manually using the gear shift lever or separate gate on the transmission.

4. Automatic transmission

Automatic transmission, as the name suggests, is a fully automatic transmission that allows the gear ratio to be changed while driving and eliminates the need for the driver to change gears manually. An automatic transmission consists of three main components: a fluid/hydraulic clutch, a planetary gear train, and a hydraulic control.

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A fluid/hydraulic clutch works similar to a manual transmission clutch, changing gears by locking and unlocking a planetary gear system. A torque converter is a famous hydraulic clutch or fluid coupling that is used in many cars with powerful engines.

The second most important part of the automatic transmission is the planetary gear train. This is a system that offers different gear ratios and changes the speed of the output shaft depending on which planetary gears are locked.

The third critical component used in automatic transmissions is the hydraulic control. It’s very similar to a fluid coupling, but it’s usually a gear pump that mounts between the torque converter and the planetary gear set and controls various clutches and belts to control the speed. output according to changes in vehicle driving conditions.

Advantages of automatic transmission

  • Driving comfort. One of the biggest advantages of driving an automatic car is its comfort. Thanks to the clutch less pedal operation and the fact that there is no need to manually shift gears.
  • Good fuel economy. Fuel economy has always been a big concern for those who choose automatic cars.
  • Designed for versatility and superior performance. Automatic transmissions are very responsive to driving maneuvers. It has enough power for quick acceleration and good driving performance. It also has a hill hold function that prevents rolling back on slopes.
  • High resale value
  • It is widely available.
  • Ideal for stop and go traffic.
  • Suitable for beginners.

Disadvantages of automatic transmission

Disadvantages compared to manual transmissions are the more space required and more weight. The main disadvantages compared to automatic torque converter gearboxes are ease of starting and high wear.

  • The purchase price is higher than the manual.
  • Higher repair cost
  • Historically, they’ve gotten worse gas mileage than manuals, but that gap is closing.


What is Automatic Transmission?

An automatic transmission is a multi-speed transmission used in motor vehicles that do not require any driver input to change gears under normal driving conditions. The most common type of automatic transmission is the hydraulic automatic, which uses a planetary gearset, hydraulic controls, and torque convertor.

How does an Automatic Transmission Work?

The most common type of automatic transmission uses hydraulic power to shift gears. According to How Stuff Works, this device combines a torque or fluid coupling converter with gearsets that provide the desired range of gears for the vehicle.

What are the types of automatic transmission?

Some of the most commonly used gearboxes in this category include:

  • Automated Manual Transmission (AMT),
  • Continuously Variable Transmission (CVT),
  • Dual-Clutch Transmission (DCT) and
  • Fully-Automatic Transmission.

What are the parts of automatic transmission?

Parts of an Automatic Transmission:

  • Transmission Casing.
  • Torque Converter.
  • Pump (aka impeller).
  • Turbine.
  • Stator (aka Reactor).
  • Torque converter clutch.
  • Planetary Gears.
  • Brake Bands and Clutches.

What is meant by automatic transmission?

Automatic transmission is a system in a vehicle that changes gears at different speeds without direct control by the driver I can’t drive her car because it has a manual transmission instead of an automatic transmission.

Is automatic transmission stick shift?

Transmissions, or gearboxes, help control a car’s speed and torque (rotational force). The higher the speed, the higher the gear needed. Automatic cars shift gears on their own, while manual cars require you to shift gears with the stick shift.

Is automatic or manual better?

An automatic car is certainly easier to drive in a stop and go traffic since it does not require too much driver input. A manual car can be cumbersome in chaotic traffic and requires a lot of driver input. However, if you want to decide which gear the car should be driven to, the manual car is a better option.

What is the difference between manual and automatic transmission?

Automatic transmission is one most people are familiar with. The automatic transmission allows the vehicle to change to different gears on its own rather than the drivers making the adjustments. Manual is where that transmission relies on the drivers to use the clutch to accelerate.

Is automatic faster than manual?

Manual cars also go faster than automatic. This can be fun, sure, but can also lead to more tickets and accidents. Manual transmissions are also a lot less complicated than automatics and are therefore less expensive to repair. But easy to fix does not mean easy to learn.

What is the disadvantage of automatic transmission?

Disadvantages of automatic transmission system: Maintenance is costly. The additional gear train is required for the reverse condition. Fuel consumption is also higher than a manual transmission. Automatic transmission consumes 10% more than a manual transmission.

What are the 1 2 3 gears in an automatic?

The numbers one two and three indicate different gears. FIRST is the slowest. The second is a little faster, and the third is faster yet. D is for DRIVE and the one you should be using most of the time.

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Is automatic safer than manual?

When you change gear, you take one hand off the steering wheel. In an automatic you can keep both hands on the wheel, meaning you have more control over your car, which is particularly important when you have to react quickly.

What does N mean in car gear?

The “N” is an indicator that your automatic transmission is in NEUTRAL or a free-spinning mode. This setting releases the gear(s) (forward and reverse) and allows the tires to spin freely. Most people do not use the N setting unless their car engine will not start and they need to push it or have the vehicle towed.

Is an automatic car good for hills?

Negotiating inclines. If you stay in an area that has a lot of inclines, then automatics can be your best buddy. Automatics come with a hill-hold that stops the vehicle from rolling backward if you come to a complete halt on an incline.

Is an automatic car good for hilly areas?

No, we won’t suggest you to go for an automatic transmission vehicle for such regions. In an automatic transmission vehicle, the change of gear takes place according to the sets of RPMs and in hilly regions, the car needs to keep at high RPS to get better results.

Is automatic car good for long drive?

An automatic transmission car actually makes a lot of sense for all those who have long commutes and often have to drive through a lot of congestion. Not having to use the clutch and the gear lever frequently reduces the driver fatigue to a lot of extents.

Why is manual transmission better?

Better fuel efficiency — Overall, manual transmission engines are less complex, weigh less, and have more gears than automatics. The end result is that you’ll end up getting more kilometers out of the petrol you pump in than you would with an automatic.

Do automatic cars use more fuel than manual?

Traditionally, automatics could use up to 10% more fuel than their manual equivalent. With modern developments in automatic transmissions and variations such as the “automated manual” now being offered on many contemporary models, there is often little to choose between the two as far as fuel consumption is concerned.

Is manual cheaper than automatic?

Cheaper – Manual transmissions have historically been cheaper than their automatic counterparts. A car of the same make and model with an automatic transmission can cost $1000 more than a manual transmission. Manual transmissions have fewer complicated parts that are easier to produce, making them less costly for you.

Why is AMT not good?

AMTs are not fuel-efficient and are costlier to maintain. In fact, there have been cases of AMT variants being even more fuel-efficient than their manual counterparts. Even the recently launched Nexon AMT and Vitara Brazza AMT are as fuel-efficient as their Manual Transmission equipped variants.

Which type of transmission lasts the longest?

Longevity. In the all-critical area of longevity, manual cars owners come out on top. When compared with their automatic cousins, most cars with manual transmission tend to last longer – a length of time that can sometimes translate to years.

What does neutral mean in a car?

Neutral isn’t necessarily a gear; it’s a state when no gear is engaged on the vehicle. In an automatic transmission, the wheels continue to spin independently of the gas pedal, so the car keeps moving.

What does S stand for in a car?

“S” is for sport. If you’re driving on twisty country roads and want to keep the RPM up as you wind through corners, the “S” position is where you want to be. In “S”, the transmission holds lower gears longer for more power as you come out of the curves.

Can I shift from D3 to D while driving?

Yes, you can switch gears from D to D3 while driving an automatic transmission car. However, it would be best to slow down a bit before switching down from D to D3 if you approach a hill.

Are automatic cars more expensive?

More expensive to buy: The main disadvantage of automatics is that they generally cost more to buy than their manual counterparts, both new and second-hand, so they’re not ideal if you’re on a budget. Boring to drive: Some drivers find that automatics take the fun out of driving.

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