Engine is often dubbed the "heart" of a car because of its great importance for the vehicle and so does the transmission. To accommodate different operating conditions of the engine, the transmission (or gearbox) needs to change the rotational speed, capacity as well as torque in order to fit the engine well.
Today, let’s take a look at our comprehensive list of types of gearbox to have a deep understanding of this indispensable part of your car.
1. What is a gearbox?
In simple term, a gearbox includes gears and gear trains to convert a certain amount of speed and torque from a device to another.
Many people often use the term “gearbox” and “transmission” interchangeably, but in fact, they slightly differ from each other, depending on where you use the term. Our explanation follows right in the next section.
Gearbox or transmission: do you use terms correctly?
2. What is transmission?
Transmission is defined as a machine in the power transmission system. Its main function is to provide controlled application of power.
In American English, the word “transmission” is exactly the “gearbox” but in British English, it refers to the entire drivetrain, which includes the gearbox, the clutch, the prop shaft (for rear-wheel-drive layout), differential and also the final drive shafts
How car transmission system work?
Like in other motor vehicles, the transmission often links to the engine crankshaft via a clutch/ flywheel/ fluid coupling and its output will be transmitted through the driveshaft to differentials. These differentials will then drive the car wheels.
The illustration of car transmission system in rear-wheel-drive layout
Besides conventional gear transmission, other alternative mechanisms such as power transformation (including hydraulic drive system and diesel-electric transmission) or torque converters can be utilized to adapt speed/torque in cars.
3. Most popular types of gearbox in cars
There are a variety of gearbox but Naijauto.com will only focus on the most common types of gearbox or transmission used in automobiles these days.
3.1. Manual transmission
Manual transmission or manual gearbox, also known as stick shift, utilizes a driver-operated clutch which, with the aid of a foot pedal and a hand lever, can regulate the amount of torque from the engine to the car transmission. The manual gearbox also uses a gear selector to be operated by hand or even foot.
This is probably the most common type of gearbox for cars and its clear advantage is the feeling of truly driving a car when you can self-select the gear and operate the vehicles by yourselves.
The stick shift gives you a true feeling of driving a car
3.1. Automated manual transmission
The automated manual transmission, in nature, is a manual-style transmission which is operated by a computer. The internal design of this gearbox is quite similar to a regular automatic with only a brake pedal and an accelerator.
Automated manual transmission is cheaper than others
So, in case you leave the transmission in D mode, it will perform like a real automatic transmission while M mode features manual mode. The decision of using the appropriate transmission in different situations totally depends on the driver.
A good point of the automated manual gearbox is that it has a lower price than others.
3.2. Continuously variable transmission (CVT)
Continuously variable transmission (CVT) doesn’t have specific numbers like 1, 2, 3 but it is still an automatic transmission. In order to change the gear ratios, normally the automatic gearbox operates by using gears which is fitted together. However, the CVT is connected by using pulleys and belts. The shift of the cheek pulleys on the secondary and primary axes will do the task.
CVT gives smooth operation but bad acceleration
The strongest advantage of a CVT is the ability to operate smoothly without delay because you don’t need to shift gear. However, this gearbox also has some disadvantages such as a poor acceleration which makes true driving fanatics feel like they're operating an appliance in lieu of driving a car. Therefore, it's more suitable for regular models.
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3.3. Dual-clutch automatic transmission
In some aspects, a dual-clutch automatic gearbox can be considered as an automatic type that owns two separate clutches. In detail, the dual-clutch transmission will provide the function of two manual transmissions in one. Despite mainly operating in fully automatic mode, some dual-clutch gearboxes can still even offer semi-automatic mode.
Most drivers of dual-clutch automatic transmission agree that this offers the best dynamic acceleration and it makes them feel a sense of luxury while driving. It’s because they are free to choose controlling the shifting by themselves or let the computer system take the rest of stuff.
Dual-clutch transmission - How it works
3.4. Torque converter
History of formation and development of this gearbox has been around for a long time. And now, it is still very popular. As its name evokes, torque converter is a part that is used to convert torque. We can simply understand that, like the role of a clutch using a gearbox, the torque converter also has an effect on transmitting power of the engine to the gearbox.
A torque converter includes turbine, gear pump, stator and one-way joint. These details are designed to reside in a shape-changing shell that resembles a circular box. The basic operating principle is that the hydraulic lines go to the pumping wheels which are available with equally aligned wings. The wings will create centrifugal force to push the oil to the side of turbine, rotating the turbine blades, then turn the gearbox.
Torque converter is durable, quiet and smooth
This gearbox has a hydraulic and mechanical constitute, speed is not too fast so it is mainly suitable for civilian vehicles. The greatest strength of this type of gearbox is a high durability, smoothness and less noise.
4. Other commonly searched gearboxes
Besides aforementioned types of gearbox, there are other terms people often search around. Let’s see how they differ from above categories and whether you should seek for cars with them or not!
4.1. Planetary gearbox/ epicycle gearbox
Planetary gear is actually a type of automatic gearbox which doesn’t have sliding dogs. It is called planetary gearbox because the system has its own sun as in the picture.
Planetary gears are locked inside the box, centered is the sun
When the sun gear is driven, surrounding planetary gears will be moved accordingly, forming the output of the gearbox. The planetary gearbox is exploited to transfer the larges torque in the form of torque density – the most compact form of it.
4.2. Worm gearbox
Worm gearbox is needed for large gear reduction. It falls into the category of right-angle gearbox and has a screw-like design.
The worm gearbox is designed like a screw
The worm gearbox can reduce the rotational speed and transmit higher torque from a piece of machine to another part.
4.3. Gear motor
Unlike mentioned gearbox, this one is a bit different in terms of applications. Gear motors are not seen in cars but mostly in devices as garage door openers, electric alarm clocks, hospital beds and even cranes.
Gear motor is a specific kind of electric motor to produce high torque but being able to maintain low speed or low horsepower.
So, the phrase contains “gear” but it might not be the type of gearbox you’re looking for.
An article only cannot cover the wide range types of gearbox as well as elaborate on how they work or what advantages they have in every application.
However, we do hope this post can help you grab basic understanding of gearbox system and be more aware of its importance inside your transport.
For car maintenance tips to make sure your gearbox is always in fit, please visit: Maintenance tips & advice from Naijauto experts