If you ask any normal individual how many types of car transmissions exist, they would probably reply “two”. The two being Manual and Automatic. Although from a broader perspective that would be more or less the right answer, however, there’s a lot more to it than just that. Yes, you’ve read that right, there are many types of transmissions out there that most of you don’t know about. Some of them might look the same from the outside or function similarly but there’s a whole lot different going on the inside. Let’s look at the most common ones.
1) Manual
Manual Transmissions, also known as sticks, have been here for a long time. They were the standard transmission option available on all road cars before any automated transmissions showed up. It consisted of a lever sticking out of the center console that one had to manually set to a particular gear depending on how fast he/she was going. In this list, manual transmissions are the only ones that used, other than the accelerator and brake, a third pedal called the clutch.
In order to shift into a gear, you had to depress the clutch pedal, put the level in the appropriate gear, and then release the clutch. The clutch was there for a smooth transition between the shiftings by temporarily disconnecting the gearbox from the engine. If you try to shift without using the clutch, you would grind the gears and that would lead to excessive wear of the gearbox.
Since everything has to be done by the driver, manual cars are considered lively and fun to drive by petrolheads. However, manuals are a dying breed as their automated counterparts are taking over the car industry. This may be the reason why many manual versions of old sports cars are rising in value as they are sought after by enthusiasts. In fact, some cars made for enthusiasts today still come with a manual. An example is the 2019 Corvette ZR1 that comes with a 7-speed manual gearbox.
2) Conventional Automatic
These were the first of the many types of automatic transmissions to be introduced into the car industry. Their early versions were slow, unreliable and were generally less desired among the petrolheads. However, they were more convenient to use compared to manuals as they eliminated the third clutch pedal and the need to shift gears manually. The computer in your car, controlled which gear you car would shift into, depending on your speed and throttle input.
Instead of a clutch, these use a torque converter. Unlike a clutch, which allows zero slippage between the engine and the transmission, a torque converter allows a certain amount of slippage to prevent the engine from stalling. This results in a significant loss of power reaching the wheels of the cars compared to a clutch.
However, conventional automatics have come a long way to the point that many performance cars still come with it. The most common performance automatic is the ZF 8-speed that comes in the Jaguar F-Pace. Some Conventional Automatics offer manual shifting but it’s not as good as Semi-Automatics.
3) Continuously Variable Transmissions
Better know as CVTs, these transmissions are really similar to conventional automatics yet a whole lot different. The similarities include the fact that your car’s computer decides the best ratio (Yes ratio, not fixed gears. Explained later) depending on your speed and throttle input. Also, they use a torque converter instead of a clutch but that’s where the similarities end.
What makes CVTs different is the fact that instead of fixed gears, they can achieve any possible gear ratio. That is possible through a belt running between two variable diameter pulleys. The gear ratio is adjusted to give you the best possible performance/fuel economy.
To better understand gear ratios, have a look at the illustration below. The left rectangle represents a conventional automatic. The gears are represented by black vertical lines. Each gear has its unique ratio and the transmission can only achieve that. It cannot access the white areas. On the other hand, the right rectangle represents a CVT. Notice all of it is black which means that the transmission can pick any ratio possible in the whole area.
This allows for a great fuel economy as your car can achieve the lowest engine RPM for any given speed. In fact, of all the transmissions, CVTs are the most fuel efficient. CVTs also have a near seamless “shifting” experience that’s great for comfortable driving. However, this makes the whole driving experience bland and is the reason why you don’t see proper enthusiast cars with CVT.
4) Semi-Automatic
As the name suggests, these are the blend between automatic and manuals. Semi-Automatic transmissions use a clutch, but instead of it being operated by the pedal, it is controlled automatically by the car. The car can also shift into gears automatically for you. However, with Semi-Automatics, you get the option of choosing to shift manually when you want to. Manual shifting is done either by the + and – signs on your shifter or by Paddle Shifters mounted behind the steering wheel.
The most common type of Semi-Automatic is a Dual Clutch Transmission (DCT). In a DCT, there are two sets of clutches that control the even and odd pair of gears respectively. How that works is that when a car is accelerating in 2nd gear, one of the clutches will already have the 3rd gear prepped up. And the moment the car shifts into 3rd, the other clutch preps up the 4th gear. This results in lightning fast shifts, faster than any other transmission.
This makes DCTs the current benchmark for performance when it comes to transmissions. Other features of DCTs include the possibility of Launch Control by pressing the brake and accelerator pedal together. Because DCTs are clutch-based, they also minimize the power loss to the wheels. However, DCTs tend to struggle in regular city driving as the shifts are often jerky at low speeds.