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  • Writer's picturejianmei huang

Everything You Need To Know About A Car's Automatic Transmission

Updated: Mar 19

Comfortable and efficient! Manual or automatic? This is one of the classic questions that many ask when purchasing a vehicle. The evolution of automatic transmissions has been spectacular in recent decades and today we can find them in different types. Below, we show you everything you need to know about automatic transmission in a car.


Motorists are divided between those who prefer manual transmission and those who prefer automatic transmission, although it is true that, in recent years, the latter has increasingly taken over the former.


There have always been all kinds of not-very-favorable comments about automatic transmissions, such as that they increase consumption, do not offer the same features, are less reliable, or that people who like to drive prefer a manual transmission. And some of that may have been true, but in times past.


However, today we do not want to review the history of the automatic transmission but rather focus on the most technical part of the matter: how an automatic transmission works, what advantages and disadvantages they offer, and what types of automatic transmissions are available.


How the Automatic Transmission Works

The first thing is to explain how an automatic transmission works and what its characteristics are. Most automatic transmissions work with a series of positions that are determined by the acronyms P, R, N, and D, to which others can be added that vary the operation of the electronics.


P (Parking): is the parking position and is used to lock the gearbox, either with the engine started or stopped, without having any gear engaged. This prevents the car from moving, even if it is on a slope without the handbrake activated.


R (Reverse): is equivalent to the R gear of manual transmissions and is used to reverse.


N (Neutral): is the neutral position. When engaged, there is no gear engaged, but unlike position P, the gearbox is not locked here, so the car will move if you don't use the brakes.


D (Drive): forward position, with which it automatically engages the gears, both up and down. Here, the driver only has to think about accelerating, braking and steering the car.


Others: in recent times, many automatic gearboxes include driving functions or programs that modify their behavior, offering greater acceleration or retention, smoother or harsher changes, etc., depending on the driver's demands. For example, Sport or ECO mode.


Currently, we can find several types of automatic transmissions on the market. Mainly, two: torque converter changes and continuous variation type.


Then there are two other changes that are more like robotic manual transmissions. We are referring to robotic and double-clutch changes. In general, we tend to call all these changes automatic, since they lack the clutch pedal.


Shift With Torque Converter

The transmission with a torque converter works through a system made up of several elements, among which the torque converter stands out, which is responsible for connecting the transmission with the engine.


The torque converter is made up of three elements inside a hermetic container: a disc-shaped pump attached to the engine, blade-shaped grooves to direct the oil, attached to a turbine which, in turn, is attached to the gearbox. of gears, and a reactor coupled to the gearbox that redirects the oil to the pump.


When the car is stopped, the pump and turbine rotate independently and, as the car moves forward, the oil flow becomes increasingly intense, until the pump and turbine rotate together. This is what is known as the torque transmission phase.


Continuous Variator-type Change

This is the change known as CVT and is present in many hybrid cars, such as those from Toyota, or in Subaru models. This type of automatic transmission is characterized by a very peculiar operation, with infinite relationships that produce what is known as the 'scooter' effect.


When you press the accelerator to the floor, the engine revs a lot, but the speed gain does not correspond to the engine speed. This problem has been alleviated in recent years through electronics, introducing a manager that simulates the relationships of a conventional gearbox.


A CVT gearbox is made up of two conical-shaped pulleys with different diameters, connected by a belt. One of the pulleys is connected to the crankshaft output and the other sends the movement to the transmissions.


Depending on the operation of the car and the driver's demand, the electronic transmission management will also vary the diameter of the pulleys. When one increases its diameter, the other decreases it, thus avoiding tension changes in the belt and varying the transmission ratios.


Robotic Changes

This is, basically, a manual transmission with an electronic clutch managed by a control unit. Through the electronics, the control unit receives numerous parameters, such as accelerator position, speed, or revolutions. With this information, the control unit determines whether the clutch should be engaged or not.


To replace the clutch and gear lever, it uses electronic or hydraulic lifters and, using an electronic calculator determines the best time to change gear.


This system also allows the driver to choose between automatic operation or manual mode, in which he decides when to change gears.


Double Clutch Transmission

In this case, we are facing another robotic manual transmission, although with nuances. Manual and robotic boxes have one clutch and two gears and the double clutch boxes have, as their name indicates, two clutches and two pairs of gear shafts, two primary and two secondary.


One of the pairs of gears is responsible for the even gears and the other pair for the odd gears, in the same way, there is a clutch for the even gears and another for the odd gears. This makes changes much faster.


When the electronics detect that it is about to shift from second to third gear, for example, before the even-numbered gear clutch disengages, the odd-numbered gear pair is already engaged, without engaging the clutch (but yes prepared).


By the time the even clutch is released, the odd clutch is already engaged and the shift occurs quickly.


Advantages And Disadvantages of Automatic Transmission

Nowadays, automatic transmissions have a series of advantages, such as offering better car performance and reduced consumption.


To this, we must add greater comfort, especially in situations of intense traffic in large cities, and safer driving, since the driver only has to pay attention to the traffic and acceleration or brake, and the mechanical safety that it provides. to the engine the smoothness of the gears.


Although not everything is positive the automatic transmission also has some drawbacks. The most important is its price: automatic cars are usually more expensive than equivalents with manual transmission.


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In addition, maintenance also tends to be more exhaustive and expensive, since they have a greater number of components.



What are the main types of automatic transmissions in cars?

Cars primarily feature two types of automatic transmissions: torque converter and continuous variable transmissions (CVT). Some models also include robotic and double-clutch transmissions.


What are the benefits of automatic transmissions over manual ones?

Automatic transmissions offer better vehicle performance, reduced consumption, and greater comfort, especially in heavy traffic. They also enhance driving safety by allowing the driver to focus more on the road.

Are there any downsides to choosing an automatic transmission?

Yes, automatic transmissions can be more expensive than manual ones, both in terms of initial cost and maintenance, due to their more complex design and additional components.


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