Generations MT, SMG, AMT, DCT/DSG in gearbox...

The transmission is one of "three main parts" of a car, which can be divided into two types: manual transmission and automatic transmission. A manual transmission mainly consists of gears and shafts that provide variable speed and torque through various combinations of gears, while an automatic transmission consists of hydraulic torque converters, planetary gears and hydraulic control systems through hydraulic transmission and gear combinations. speed and torque. There are four common types of automatic transmissions: hydraulic automatic transmission (AT), mechanical continuously variable automatic transmission (CVT), electronically controlled mechanical automatic transmission (AMT), and dual clutch automatic transmission (DCT). Since AT is widely used in family cars, AT has become almost synonymous with automatic transmission. Today editor will tell you about specifics of each gearbox.

Manual transmission (MT)

Manual transmission, also known as manual transmission, is to manually move gear lever to change meshing position of gears in gearbox and change gear ratio to achieve purpose of speed change.


The structure of manual transmission is simple, maintenance cost is relatively low, transmission efficiency is high, fuel economy is good, it is relatively economical and driving pleasure. Disadvantage

The operation is cumbersome, especially when driving in city. Driving with a manual transmission is more time consuming and tiring. In a city surrounded by walls, you have to frequently depress clutch and change gears, which is very troublesome. If you are a beginner, this will be even more confusing.

Manual transmission imposes relatively high technical requirements on drivers, in absence of operating skills it is easy to turn off engine halfway, and even fuel consumption will be higher than that of models with automatic transmission. In addition, city roads are now becoming more and more congested, and there are a lot of red lights on streets, which require frequent starts and stops, it takes a long time to drive manual transmission with half clutch, and left leg will be very tired.

Suitable for crowd

Good driving skills, rarely drive around city, hope to buy a car at a lower price and enjoy driving.

As name implies, a manual transmission requires driver to change gears himself and at same time interact with left clutch pedal. It is based on engagement of driving and driven gears of different diameters to change torque. Each gear has a pair of primary and secondary gears with a specific gear ratio, and gears of each gear are always meshed and rotate together. With help of synchronizers and shift forks, gearbox output shaft selects speed and torque in any gear. The shift lever operated by driver is actually designed to control movement of shift fork. Although operation of a manual transmission is complex, it allows driver to participate in it for more driving pleasure. Not only that, structure of manual transmission is simple and failure rate is low, so that it still has strong vitality in today's highly advanced automatic transmission technology.

Automatic transmission (AT)

An automatic transmission, also known as an automatic transmission, operates on basis of a planetary gear. It can automatically change speed according to degree of accelerator pedal and vehicle speed. The driver only needs to press accelerator pedal to control speed of vehicle. Generally speaking, hydraulic automatic transmission is most common automatic transmission.


Compared with manual transmission, operation of automatic transmission is relatively simple, comfort is good, driving is easy, and there is no need to press clutch, even if left foot is off, it can be controlled. .


The cost is higher than manual transmission, transmission efficiency is poor, shift response time is relatively long, and fuel economy is poor.

For conventional automatic transmissions, it is not realistic to completely eliminate shifting frustration. With heavy throttle, even a 6-speed transmission can still feel shifting kickback. In addition, driving pleasure is relatively low, do not expect feeling of integration of people and vehicles, but power is at ready. Compared to models with a manual transmission, fuel consumption will be higher, for example, for same vehicle, an automatic transmission usually has a higher fuel consumption than a manual transmission.

Suitable for the crowd

Car owners who enjoy simple and comfortable driving, and car owners who spend most of their time in crowded cities.

Automatic manual transmission (AMT)

Many will mistakenly think that AMT is closer to an automatic transmission in terms of its structure, but in fact its structure is still same as that of a manual transmission, only on this basis an automatic switching mechanism has been added to replace driver’s hand and foot over fork and clutch. Here you can clearly understand, as if there is a small robot helping to shift gears and press clutch to control manual transmission. However, because shifting speed of automatic shift mechanism is relatively slow, there will be a serious loss of power at moment of shifting, and feeling of frustration is relatively strong, which is criticized by many car owners. short.

Automatic manual transmission

An automatic manual transmission, as name suggests, is a type of transmission that combines two modes of manual and automatic shifting. There is an essential "+

on this type of reducer

/-", and some even have paddle shifters that allow you to shift gears without taking your hands off wheel.


Choose according to your needs: choose automatic transmission mode if you want easy driving, and switch to manual transmission mode if you want to enjoy driving.


Relatively high price, poor fuel economy

When gear is placed on gear D, it is a normal automatic transmission model. If you want to enjoy driving, you can select gear yourself by operating shift lever or paddle shifters without pressing clutch, which is more convenient than a manual transmission. For example, on a long downhill, you can select a lower gear and use engine's braking power to control vehicle's speed so you don't have to apply brake for a long time to slow down. brake pad wear. Generally speaking, an automatic manual transmission is still an automatic transmission that can partially realize a mechanical function, but it is still different from a pure manual transmission.

Suitable for crowd

Car owners who primarily use car in urban areas and want it to be easy to drive while maintaining some driving enjoyment have a better economic opportunity.

Dual Clutch Transmission (DCT or DSG for short)

Double clutch is a rather controversial design. Many people understand her because of defective Volkswagen DSG incident found at 315 party a few years ago. In fact, design idea of ​​the dual clutch is not complicated, and this is also an automatic transmission design that was invented relatively early. Its structure is same as that of a manual transmission, but there are two sets of clutches, one for odd gears and other for even ones. When gear is in an odd gear, even gear is already in ready state, so it can be shifted in shortest possible time when shifting up and down. You can visually understand that there are two small robots that help you shift gears and press clutch at same time, one is responsible for shifting odd gears and other for shifting even gears, so efficiency is twice that of AMT. There are a lot of heated discussions on Internet that dual clutch box causes a strong feeling of disappointment, but in fact, objectively speaking, when dual clutch box does not fail, smoothness of shifting is quite good, and so-called strong disappointment is actually malfunction. The usual logic of a keyboard player's thinking is to define general characteristics of a design with a low probability of failure.

Automatic transmission (AT for short)

Finally, it comes to a real automatic transmission, its internal structure and principle is completely separated from design of a manual transmission. The change in torque no longer depends on engagement of driving and driven wheels, but is mainly carried out through torque converter and planetary gears. In addition, it cooperates with control unit, electromagnetic control mechanism, multi-plate clutch, etc., forming an automatic gear shift mechanism. Due to presence of planetary mechanism, automatic transmission can cover a very large range of gear ratios, and in order to compensate for gap in gear ratio between gears and reduce shift frustration, number of gears is also increased. For example, classic BMW 8-speed automatic transmission and Mercedes-Benz 9-speed automatic transmission. The AT often also has a manual mode, but when you manually shift up and down you don't actually take control of gearbox directly but send a shift signal to computer and it still has final say on whether it will work according to your intention. In fact, this so-called manual is just a homemade computer-generated experience to keep you entertained and coax you into playing. The automatic transmission is design with best integrated performance at present, but due to complexity of its design, maintenance cost in case of failure is also most expensive.

Continuously Variable Transmission (CVT for short)

The continuously variable transmission consists of two types of variable speed discs and a drive belt. Therefore, it is simpler in design and smaller in size than an automatic transmission. In addition, it can freely change gear ratio to realize whole stepless transmission process, so that vehicle speed changes smoothly, without feeling of "stopping" when shifting gears in traditional gearboxes.


The most obvious benefits of a CVT are smooth running, good fuel economy, stable power output and high comfort.


Low torque, weak starting acceleration and poor handling

The design and technology of continuously variable transmission is more complex and advanced, and its maintenance cost is higher than conventional automatic transmissions. In addition, due to small size and CVT's inability to provide high torque power output, generally speaking, an engine with a displacement of more than 3.0L cannot be matched with a CVT continuously variable transmission.

Summarizing, we can say that design of reducer is very complex, and differences between different types are quite large, I tried to organize and summarize it in a brighter and more popular languageycom. However, regarding advantages and disadvantages of different gearboxes, we can only say that each has its own advantages and disadvantages. As for whether it is possible to choose 1234, because everyone has different needs and hobbies for cars, it is naturally impossible to make an objective and fair judgment.