Have you ever heard the word “transmission”? If you like cars or are used to car maintenance, you probably know that, but in general, many people don’t know much about transmissions. Among the transmissions, there are not only AT and MT, but also CVT, DCT, AMT, etc., and their structures and mechanisms are also different. Here, we will comprehensively explain the transmission, including the basics of the transmission, the type of transmission, the guideline for replacement, maintenance and inspection, and the measures to be taken when an abnormality is found.
What is a transmission?
A car is equipped with various parts, one of which is called a transmission. A transmission is a power transmission device that consists of gears and shafts of various sizes and transmits the driving force output from the engine to the wheels. Also known as a transmission.
What is the role of transmissions in automobiles?
The transmission plays the role of creating the necessary driving force by changing the gear according to the driving situation of the car. For example, on a steep uphill, the gear is changed to a low speed gear to reduce the number of revolutions, and when traveling fast on flat ground, the gear is changed to a high speed gear to increase the speed. It’s easy to imagine that it’s the same as a bicycle gear change. By doing this, the load on the engine can be reduced and the car can be operated efficiently, resulting in better fuel economy.
The performance of automobiles has evolved with the times, and various transmissions have been developed in recent years. Typical transmissions include manual transmissions (MT), in which the driver manually shifts gears, and automatic transmissions (AT), in which the machine automatically shifts gears. In addition, there is a continuously variable transmission (CVT) that can change gears steplessly without using a speed change gear, an automatic manual transmission (AMT) that automates shift changes for MT vehicles, and a seamless two-clutch transmission. Dual clutch transmissions (DCTs) that enable shifting have also been developed and are used in many vehicles.
MT: What is a manual transmission?
MT (manual transmission) is a type of car that changes gears manually, and various gears such as neutral, reverse, 1st to 6th gear are prepared, and 7th gear or more is prepared in it. in some cases. It is often called simply a manual, but it is also called an MT car or mission. Today, it is installed in some sports cars, commercial trucks, and work vehicles.
MT: What is the structure / mechanism of a manual transmission?
Shifting the manual transmission involves clutch operation. When the clutch pedal is depressed, the drive transmission between the engine and transmission is cut off, and the drive force from the engine is not transmitted. If you change gears in this state and release the clutch pedal again, the engine and transmission will be reconnected, so power will be transmitted. In addition, the synchromesh mechanism is adopted in the manual transmission except for a few vehicles. The synchromesh mechanism is a mechanism that synchronizes the rotation of axes with different rotation speeds, which makes it possible to smoothly change gears.
AT: What is an automatic transmission?
AT (automatic transmission) is a car with a transmission type that allows the machine to automatically change gears that the driver had to operate by himself, and is generally called “automatic”. It is called.
AT: What is the structure and mechanism of an automatic transmission?
The automatic transmission has several gears, and it automatically changes to the optimum gear by hydraulic control each time according to the engine speed, speed, accelerator opening, etc. Also, there is no clutch pedal in the manual. It has a function that allows you to change gears and transmit power without having to disengage the clutch. The automatic transmission is equipped with a device called a torque converter instead of a clutch and is used for power transmission. This device is located between the engine and the automatic transmission and is capable of transmitting power through the oil contained therein. In addition, it is not as explicitly engaged or disengaged as a clutch, so it is always driven when the engine is starting. As a result, the car creeps forward even though you have not stepped on the accelerator, so you need to step on the brakes all the time when you stop.
CVT: What is a continuously variable transmission and how does it work?
A CVT (continuously variable transmission) is a transmission that uses a special metal belt instead of a combination of gears. Since you can shift gears without using clearly separated gears like 1st to 5th gears, you can shift smoothly. In addition, since the gear ratio can always be set to match the running speed of the car, fuel efficiency can be improved while making the best use of the engine output.
AMT: What is an automatic transmission manual transmission and how does it work?
AMT (Automatic Transmission Manual Transmission) is a mechanical automation of manual clutch operation and shift change, and is also known as “semi-automatic”. In addition, the structure is a basic manual transmission, so it is very simple and lightweight, has good power transmission efficiency, and has good fuel economy when driving. However, since it is a manual that automatically shifts, a slight shock called a shift shock will occur at the time of shift change. Therefore, it lacks smoothness when shifting.
DCT: What is a dual clutch transmission and how does it work?
The basic mechanism of DCT (Dual Clutch Transmission) is almost the same as the manual. The difference is that the DCT has two clutches, and the gears that each is in charge of are divided into odd-numbered gears (1-3-5th gear) and even-numbered gears (2-4-6th gear). The mechanism for changing gears is to put the even-numbered gears on standby in advance while using the odd-numbered gears. This allows you to shift up instantly. The DCT has been widely used in sports cars in recent years because it allows you to enjoy a driving feeling that is as direct as a manual.
Position of transmission mounted on the car
If you know the structure and mechanism of the car, you may be able to repair or modify it yourself. Here, we will explain the position of the transmission for each FF car, FR car, MR car, and RR car.
Transmission mounting position of FF vehicle
In front-wheel drive vehicles, many of the major machines such as transmissions are mounted under the hood. In addition, most FF vehicles are characterized by the fact that the engine and transmission are arranged vertically (horizontally) with respect to the vehicle body. As a result, a large interior space can be secured, so FF vehicles are used in many compact cars.
FR vehicle transmission mounting position
In FR cars, the main machinery such as the transmission is mounted on the front of the car. In addition, the front wheels are used for steering and the rear wheels are used for driving, and the steering is not disturbed by the driving force, so a straightforward steering feel can be obtained.
MR car transmission mounting position
In MR cars, the engine and transmission are located in front of the rear axle. Due to its high acceleration performance, it is often used in race cars such as F1 and supercars.
RR car transmission mounting position
RR vehicles have major machinery such as engines and transmissions located directly above or behind the rear wheels. It was widely used in commercial vehicles from the 1960s to the 1970s, but it is almost gone now due to the progress of development of FF vehicles.
Transmission points when choosing a car
When you decide to buy a car, you may be wondering whether to buy an MT car or an AT car. For such people, we have summarized the advantages and disadvantages of MT cars and AT cars.
Advantages and disadvantages of MT (manual) cars
The advantage of MT cars is that you can use the accelerator and clutch to operate the car as you wish, so you can enjoy the “feeling of driving”. Also, because there is a clutch, there is almost no possibility that the car will start suddenly even if you mistakenly step on the brake and accelerator. Furthermore, although it depends on the model, MT cars have a simpler structure inside the gearbox than AT cars, so it can be said that the car body price tends to be cheaper. On the other hand, the disadvantage of MT cars is that the burden of operation increases due to gear changes and clutch pedals operated by foot. Also, be aware that if you make a mistake in the operation, it may cause an engine stall.
Advantages and disadvantages of AT (automatic) cars
The biggest merit of AT cars is that they are easy to operate because the gear change is automatic. Most operations can be performed with just the steering wheel and brake / accelerator, making driving easier. Another merit is that the specification makes it difficult to lower when starting on a slope due to the “creep phenomenon” in which the car moves forward without stepping on the accelerator. However, as a disadvantage, if you make a mistake in stepping on the accelerator and brake, mistakes such as sudden start are likely to occur, so you need to be careful when driving. Also, because the gears shift automatically, you cannot control them in detail, so some people may be dissatisfied with the fact that they don’t feel like driving a car.
Importance of transmission oil
If you have a car, changing the engine oil will be familiar to you. However, many people may not be familiar with changing transmission oil. Here, we will introduce the role of transmission oil, a guideline for when to replace it, and how to replace it.
The role of transmission oil
Inside the transmission of a car, multiple gears operate in complex movements. Among them, transmission oil plays a role as a lubricant to prevent gear wear.
Estimated timing for changing transmission oil
If you continue to use transmission oil for a long period of time, the performance of the oil will deteriorate, and the gears will become poorly lubricated and will wear out and be scraped. Therefore, it is necessary to change the transmission oil regularly because it may lead to problems such as poor gear engagement, poor fuel economy and poor acceleration performance. Regarding the time to change such transmission oil, it is generally said that the mileage is 20,000 km or once every two years. If you change at this pace, you can maintain a clean oil condition. If you’re not driving that much and the gears aren’t in the right gear, it’s likely that the gears are worn. We recommend that you change the mission oil immediately and check the gear if necessary.
How to change the transmission oil
Changing the transmission oil is not that difficult and you can do it yourself. The following five tools are required for replacement.
・ Waste oil treatment box
・ Kerosene pump
・ Drain plug wrench
・ New mission oil
The procedure for changing the transmission oil is described below.
1. 1. First, lift the car body using a jack.
2. Next, loosen and remove the filler bolt, and then remove the drain bolt.
3. 3. Drain the old oil into the waste oil treatment box from where the drain bolt was removed.
Four. After draining the old oil, tighten the drain bolt, and then use the kerosene pump to add new oil from the filler bolt.
Five. Finally, tighten the filler bolts and jack down to complete.
You can replace it by following the above procedure. When changing the transmission oil, it is often troublesome to jack up or dispose of old oil, so in order to change it more reliably, it is recommended to have it changed at a maintenance shop or car dealer. I recommend it.
Dangers and remedies for transmission oil leaks
If oil leaks from the transmission, it will be poorly lubricated and, in the worst case, you may not be able to drive. Therefore, if an oil leak is found, it needs to be repaired immediately. Of course, if the amount leaked is small, replenishing the oil will temporarily overcome it, but that is not the ultimate solution. If oil leaks, we recommend that you have it inspected and maintained at a maintenance shop or car dealer.
Transmission maintenance / inspection method
It is an indispensable transmission for moving a car, but if you can maintain and inspect it yourself to prevent troubles, you can ensure safety. We will explain how to maintain and inspect the transmission separately for MT and AT.
What is the MT (manual transmission) inspection method?
MT inspection methods include inspection of shift levers, clutch pedals, clutch fluids, and transmission oil.
1. 1. Checking the shift lever
When inspecting the shift lever, check whether the car can actually be driven and the shift can be changed smoothly, and whether any abnormal noise or abnormality has occurred.
2. Inspection of clutch pedal
Check if there is play with the clutch pedal, and also see if the space with the floor is properly maintained. At the same time, check whether the clutch pedal can be depressed smoothly.
3. 3. Inspection of clutch fluid
The clutch fluid is inspected in the reservoir tank in the engine room. There are upper and lower scales on the side of the reservoir tank, so check if there is fluid between the scales and pay attention to the color. If it has a turbid brown color, it is better to replace it.
Four. Inspection of transmission oil
Transmission oil does not have a scale that allows you to check the amount of liquid, so you can just open the filler plug, which is the oil inlet, insert your fingertips, and touch the oil.
If you carry out these inspections and find any abnormalities or abnormalities, we recommend that you have them inspected at a maintenance shop or car dealer as soon as possible.
What is the AT (Automatic Transmission) inspection method?
Inspection methods for AT include inspection of automatic transmission fluid (ATF).
1. 1. Inspection of automatic transmission fluid (ATF)
After actually driving and warming the ATF, keep it in each range such as R, D, N for a few seconds with the engine running, and return it to P when shifting to all ranges. Next, remove the ATF level gauge in the engine room, wipe off the ATF adhering to the gauge with a cloth such as a waste cloth, put the gauge back in again, and check the liquid level. The gauge has HOT and COLD scales, but it is okay if the ATF adheres between the upper and lower lines of the HOT. Also, pay attention to the color of ATF at that time. Normal ATF has a highly transparent red color, but if there is any problem, it turns brown or black.
2. Actually drive the car and check the timing of shifting etc.
In addition, please check if there is any discomfort in the timing of shifting and if there is any abnormal noise when you actually drive.
If you carry out these inspections and find any abnormalities or abnormalities, we recommend that you have them inspected at a maintenance shop or car dealer as soon as possible.
What to do in case of transmission failure / abnormality
I don’t want to imagine, but while driving a car, the transmission may break down or become abnormal. Introducing how to deal with failures and abnormalities that are useful in such cases.
Causes and remedies when the transmission warning light comes on
The transmission warning light is lit when there is a behavior or abnormality in the transmission system that is not normally possible. When this light comes on, it moves in fail-safe mode, so the gears are fixed in place and you can’t control low or high speeds. However, it is in a state where it can be moved, so avoid sudden starts and accelerations, and immediately bring it to a car dealer or maintenance shop.
Causes and remedies for abnormal noise from the transmission
The cause of the abnormal noise from the transmission may be that there is a problem such as damage inside the transmission. If a problem occurs in the mission, you may not be able to change the shift and you may not be able to control the car, which is very dangerous. Driving a car with damage to the mission can also cause more serious damage. Therefore, if you notice any abnormal noise, immediately request a car dealer or maintenance shop for repair and inspection.
Causes and remedies when the transmission does not work
There are cases where the transmission breaks down and becomes stuck due to long mileage, repeated unreasonable driving, metal fatigue, etc. The best way to deal with this is to have a car mechanic or dealer repair it instead of trying to fix it yourself. Also, depending on the degree of breakdown, the repair fee may be expensive, so it is a good idea to take the plunge and buy a new car.
What is the difference between an automatic and a manual gearbox?
How does the system automatically change ratio?
The main differences of an automatic gearbox compared to a manual gearbox consist of the following 2 points
In the nature of the system , as the automatic gearbox is a hydraulic system, while the manual one is a mechanical system, consisting of arms and levers
In the implementation (as the term itself says, in an automatic gearbox the change of the ratio occurs automatically, while in a manual one it is implemented by the operator)
The automatic change of the gear ratio takes place via a system of hydraulic actuators . The input shaft, connected to the engine by the torque converter (the clutch of automatic gearboxes, we will see later), acts as a pump, thus moving and sending a working fluid (usually oil) under pressure. When a certain pressure is reached, the opening of a butterfly valve will be generated, which in turn will activate an actuator which, with its movement, will cause the variation of the inserted ratio. Following the gear change, the engine speed will drop accordingly: this will result in a drop in pressure and a valve closing.
How does the torque converter work?
A question that remains unsolved is how the automatic gearbox can replace the “detachment of the clutch”. In a manual transmission car, the manually operated clutch connects the shaft coming out of the engine to the shaft entering the transmission. The motion is transmitted through the contact between 2 discs, triggered in normal conditions but which can be defused by pressing the appropriate pedal.
In an automatic transmission car, the role of the clutch is replaced by the torque converter . It has as its working principle the exploitation of the viscosity of a fluid for the transmission of motion. Instead of the two discs (present in the clutch) there are two impellers immersed in a fluid: if the machine “idles”, there will be no transmission as the drag force of the liquid is not sufficient to make the vehicle move, while in conditions of motion the viscosity of the fluid is such as to be able to transmit the torque from the crankshaft to the gearbox.
In other words, the impeller connected to the motor causes the working fluid to “vortex”: the movement of the fluid itself will induce motion in the impeller connected to the gearbox.
Today, various types of transmissions have appeared and are installed in cars. Many people don’t usually care about the transmission, but like the engine, it is a place that controls the functions that are very important for driving a car. In addition to regular inspections, if you feel something is wrong with the transmission, please ask a specialty store for inspections and repairs for your safety. From a mechanical point of view, therefore, the converter will be a tray containing the 2 impellers, the transmission fluid and a stator, that is a non-rotating bladed disc, placed between the 2 impellers, which diverts the flow between the first and the second. in order to “optimize” the transmission itself as much as possible.