Transmissions Explained, Auto, CVT, Dual Clutch and Manual

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kingr
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Transmissions Explained, Auto, CVT, Dual Clutch and Manual

Post by kingr »

Whether you are buying a new or used car, you will often hear about the different types of transmissions on offer. Some cars have manual transmissions, while others have automatics. You might even have heard of a continuously variable transmission (CVT) or a dual clutch transmission. What do these terms mean and what’s the difference between them?

Firstly, we need to answer the question of why does a car need a transmission in the first place?

Internal combustion engines work at a relatively high rotational speed that has to be kept within a certain bracket for optimal performance. The transmission is the way to deliver the power created by the engine to the driveshaft, without changing the engines operating speed too drastically. So the transmission is the “middleman” between the power created by the engine and the power that drives the wheels. It is a device that uses gears of different ratios, as well as gear trains to provide speed and torque conversions from one rotating power source to another. The manual gearbox was the first form of transmission developed, but as technology progressed, the complex automatic gearbox came into being. After that, the CVT transmission came into effect to simplify the whole process, as well as to cut costs. Lastly, the dual clutch system was introduced, especially on performance cars, which require gear changes to be as seamless as possible. So here are the main transmission types explained so you can be informed when investing in a car.

Manual Transmission

The manual transmission was the first to be introduced, with most cars having only three gears at the time. Because the internal combustion engine can only work optimally within certain revolutions per minute RPMs, there was a need to distribute power without affecting the engine speed. The way that a manual transmission works is by having a number of shafts, normally two or three that run parallel to each other, with one linked to the engine and rotating at the engine speed.
The shaft is linked to another shaft through different-sized gears than lock together with through the use of teeth. By having different-sized gears locking together, it creates a “ratio” depending on the size of the gear selected. This means that while the engine is working within a certain bracket of revs, depending on the gear selected, it will only be able to perform within a certain limit. When changing gears, the engine has to be moving at a certain speed before a gear can be selected, and it has to be done through the clutch. Without a clutch, the engine and wheels would be directly linked and the wheels would turn even if the transmission was in neutral. It also makes it easier to change gears when the car is moving because when the clutch is pressed, no torque is transferred from the engine to the transmission, so the next gear can be selected.

Manual gears, once the most popular, even for performance cars are mostly dying now. An example is the new BMW 3 Series which the first 3 series with no option of a manual transmission. Due to its old design, it is still used for more budget-friendly cars and the odd performance car, but year by year it is being surpassed by other transmissions. Some of its distinct advantages such as great fuel economy and quick changes have been surpassed by CVT and dual clutch transmissions. Although it is dying, with more and more manufacturers no longer using them, they still have a huge following, especially by people who enjoy the shifting on performance cars like the Volkswagen Golf 6 GTI and BMW E46 M3.

Automatic Transmission

Automatic transmissions have the same operating principle to the manual transmission in that they are a “middleman” between the crankshaft, and the power actually going to the wheels of the car. The first automatic transmissions came out as early 1900’s, but they were still in their crudest form and weren’t reliable. Instead of having different sized physical gears, which have to be lined up by pressing the clutch, the automatic gearbox has sensors which determine when it should change gears. The gearbox itself has something called Epicyclic, or planetary gears, which has two gears mounted so that the centre of one gear revolves around the centre of the other and are on one central shaft. So instead of having a dedicated gear wheel for each gear, the automatic transmission does it through combinations of gears, For example, the outer ring could be moving while the inner gear remains stationary. Instead of having a physical clutch, the automatic has a torque converter which uses transmission fluid to turn the turbines, which changes gear as more pressure is put on it.
Early automatic transmissions were very complicated, unreliable, and had a reputation for increasing the car’s fuel consumption. They also couldn’t launch, or change gears fast enough for performance cars. Things have changed a lot since then and they are now very popular, especially for vehicles which require high torque such as 4x4’s. The attraction of automatic gearboxes is that they make driving much easier. There’s no need for the clutch pedal, and once the car is in drive mode, all the driver has to do is accelerate and brake and the gears will automatically change. Due to needing transmission fluid to function well, it’s advisable to have the fluid replaced regularly as recommended by the manufacturer to extend the life of your car.

CVT Transmission

Continuously Variable Transmission (CVT) has also been around for a long time but has only become popular in cars over the last few years. In principle, it does the same work as the manual and automatic transmissions but uses a completely different system to get the job done. A CVT is made up of a pulley system, with cones at each end of the pulley with a chain belt running in the middle. The cones then move together or apart to increase or decrease the diameter at which the belt operates. So instead of having physical gears with teeth like the manual and automatic, when a CVT needs to transfer power to the car, all it does is increase and decrease the space between the cones to change the diameter at which the belt turns. It works with sensors which detect the accelerator pedal position, engine speed, as well as vehicle speed to decide how to control the movement of the pulley.

CVT transmissions are much simpler and cheaper to manufacture than conventional gears and are becoming more and more common. One of their main benefits is that it always matches the engine’s rev speeds, whether moving slow or fast. Since the ratios are always changing, CVT’s often feel like they are moving in just one long gear, and can sometimes be loud when accelerating. Modern CVT transmissions are also more economical than normal “fixed ratio” cars. Since CVT transmissions don’t deliver the best torque, they aren’t used much on 4x4’s or very high-performance cars. CVT transmissions are notoriously expensive to repair and the fluid should be changed regularly to ensure that they run smoothly. If your vehicle isn’t under warranty, it’s worthwhile getting an extended warranty to protect against the high costs associated with transmission problems.

Dual Clutch Transmission

A dual clutch transmission (DCT) is a combination of both a manual and an automatic gearbox. A DCT uses a clutch plate like a manual transmission but has two separate clutches in one housing, one for odd numbered gears, and one for even numbered gears. Instead of the driver selecting the correct gear to drive in like a manual, the dual clutch changes the gear automatically when the computer senses that a gear change is required. DCT is very heavy and complicated to manufacture and some can work like normal automatics, while others can work like manual transmissions with paddle shifters or an alternative gate on the gear selector. Dual clutch transmissions tend to yield improved fuel consumption and are easy to drive at very slow speeds without the gears slipping

Because the next gear is always preselected, the dual clutch transmission can change gears faster than any other types of transmission and that’s why they are mainly used in performance cars. Many driving purists complain about the lack of driver involvement when driving a performance car with a DCT, but manufacturers such as Lamborghini and Ferrari are using them exclusively and have phased out the old manual transmission from their cars.

These are the four main types of transmissions that are found in modern day cars. The manual, once the most popular is finally getting retired, while the cheaper and more economical automatics and CVT cars take over. Since the dual clutch transmission is complicated and expensive, they are mainly used for high-performance cars.

Whether buying a new or used vehicle it is advisable to check what transmission the car has, and also if the transmission has been serviced or had any work done to it. It is always advisable to also check the VIN number to make sure that everything is in order as well as doing a vehicle valuation to ensure that the price is worthwhile. Wheelindex has these tools and more to make the decision of purchasing or selling a car much simpler and easier.
Kurt #3337

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Ex: 07" G5 GTi, 13" ST180, 03" Mk4 2 door 1.8T Stage 2, 07" Velo 1.6, 83" Mk1 GT 2.0 8v MP9, 87" Mk1 1.6 CitiSport, 88" Mk2 2.0 16v, 83" Mk1 GT 1.6 + 40 webers
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Unobeat
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Re: Transmissions Explained, Auto, CVT, Dual Clutch and Manual

Post by Unobeat »

Great read, nice write up.
THANAS wrote:Mix them together to create Shellstrol, and then mix that with Winstrol to create the ultimate, maximum performance oil for your engine.
panic-mechanic wrote:When I build engines and do stuff like this I do it when there is nobody else around, No distractions, No phone nothing so that you don't forget what you should be doing. It's the little things that make them run right. Anybody can slap a basic bottom end together. that is the easy bit. It's all the little things that makes these builds a success or not.
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kingr
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Re: Transmissions Explained, Auto, CVT, Dual Clutch and Manual

Post by kingr »

Unobeat wrote:Great read, nice write up.
Thanks, much appreciated.

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Kurt #3337

Current:
- 10" Mx5 NC2 (main daily)
- 12" Toyota Hilux D/C 2.5tdi 4x4 (tow car / vacay)
- 2020 Mini Cooper S Clubman (swambo)
- 80" VW Mk1 2 Door Golf 8vt project 192wkw/314nm

Ex: 07" G5 GTi, 13" ST180, 03" Mk4 2 door 1.8T Stage 2, 07" Velo 1.6, 83" Mk1 GT 2.0 8v MP9, 87" Mk1 1.6 CitiSport, 88" Mk2 2.0 16v, 83" Mk1 GT 1.6 + 40 webers
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