What are the different types of transmission and how do they work ?

Educational

Oct 13th, 2019

What are the different types of transmission and how do they work ?

Have you ever noticed that some cars differ in pedal and gearbox arrangement from the one in your car? The difference lies in the type of transmission system that each vehicle uses.  

So what is a car transmission?


A transmission system is the part of your automobile that transmits the power from the engine to the drive wheels. Without it, this power will be of no use to the car. Think of it as a gearbox or a system of gears that converts the engine's output to speed and torque. 

The transmission reduces crankshaft rotations to a rational value using interlocking gears. This ensures that the generated torque is used effectively and the engine operates at an optimum speed.

Back in the day, all automobiles used manual transmission, but technological advancement has brought about different car transmission types. Aside from the commonly used types like automatic and manual transmissions, there are several other types or subtypes. This article will discuss these various types and how they work to give you a working knowledge about how they differ from each other. 

Types of Car Transmissions


1. Manual Gearbox

The manual type is the simplest and earliest gearbox type, although modern transmission types are slowly supplanting it. With the manual transmission, a driver-operated clutch forms the link between the transmission’s input shaft and rotational energy from the engine. 

Alongside the clutch, there is a movable gear selector that the driver uses to engage a fixed set of gears. The selector fork connected to the shifter can be operated using a right hand or left hand depending on the car drive model. 

The clutch, on the other hand, is operated by the driver's foot and has different output reactions depending on the input action. It’s a coupling device that allows you to change gears by separating the engine from the transmission.

When fully pressed, it allows you to change gears or to stop the car. As the driver releases it, torque is transmitted. The engine rotates now while adjusting to the selected gear. The clutch slip is also used to start a stationary vehicle. Releasing the clutch allows for full engagement. In turn, all the generated torque is transmitted under the new gear. 

Over time, this transmission has earned different phrases and names like 'stick shift' and 'standard'.

2. Automatic Transmission

Most vehicles today come with an automatic transmission system due to the convenience and ease of use that it offers. Instead of the manual clutch, what it has is a torque converter for converting and transmitting the engine's power. A torque converter includes an impeller, a turbine, and a stator in between the two.

The stator builds up the speed of the fluid by directing most of it to the impeller, which in turn helps drive the turbine. When under pressure, the fluid acts on the brakes and clutches.

The driver’s work is to select between the P-R-N-D-L options. P represents 'Park’ which, as the name suggests, stops the car from moving when parking. Take note that consistent use of P may bring wear to the gearbox. R represents 'Reverse’ which allows the vehicle to move backward. N stands for the 'Neutral’ mode, which decouples the transmission from the engine. D represents 'Drive’ which lets the car move forward.

The vehicle’s computer automatically does gear shifting using a planetary gearset and clutches. Instead of the mechanical clutch, the gearbox uses a fluid housed in a doughnut-shaped chamber to connect the engine to the transmission. Gears are always engaged in this transmission; hence, there's a smooth gear selection.

A Tiptronic transmission, aka manumatic, works as a manual gearbox but uses a torque converter instead of a clutch pedal. Options to switch to fully automatic or manual mode are available.

3. Continuously Variable Transmission (CVT)

A CVT offers just about the same experience as an automatic but works differently. Unlike other types, a CVT does not use gears. Instead, it uses a belt-and-pulley system to give a smooth transition between gears.

Notably, the absence of a fixed gear gives CVT its advantages over other transmissions. CVT allows for an infinite range of ratios and uninterrupted transfer of power to wheels. Additionally, it enables the engine to rotate at maximum speed. 

The car’s computer decides how to vary the pulley system to determine the optimal ratio for the current driving situation. The result: fuel economy. No other transmission type at the moment offers a better mile per gallon ratio than CVT.

 The downside, however, is that the engine can produce loud noises.  At the same time, car aficionados feel that the seamless acceleration and smooth operation without manually shifting gears takes the fun out of driving.

4. Automated Manual Transmission

An automated manual transmission is also known as semi-automated transmission. It is a hybrid of both automatic and manual transmission. 

This transmission works with a mechanical clutch. However, the driver does not manually control it but instead operates it using sensors, actuators, and pneumatics. This transmission is becoming less common in the market, however. 

The engines in vehicles using this transmission type have a jerky performance at relatively low speeds. However, over long distances, they have high gas mileage.

5. Dual-clutch Transmission

A dual-clutch transmission is also a combination of both the manual and automatic types. It makes use of two shafts with separate clutches for even-numbered and odd-numbered gears. There is no torque converter in a dual-clutch transmission. 

The first gear to shift to is pre-selected while the car is accelerating. The computer then chooses the next gear simultaneously while engaging the first. Its main advantage is that it allows you seamless downshifts.

It is considered a dry type of transmission as one doesn’t have to swap out the gearbox fluid. This transmission is associated with noise, stalling and throttle response problems, and thus requires regular maintenance.

Direct Shift Gearbox (DSG) works the same way as DCT except that it disengages a clutch that is not in use.

Depending on the driving needs, the choice of transmission to use rests entirely on an individual.


Sam O,