If you’re not too familiar with the mechanical workings of cars, you wouldn’t be faulted for not understanding the different kinds of acronyms that pop up whenever you look at a brochure or read an article. While this is usually a problem when it comes to the hundreds of different safety system names, we also see this with different transmission options for cars – but fret not, we’re here to help!
In this piece we’ll break down the various common transmission types you’re going to see in everything from a mass market commuter car to a high end luxury hypercar – barring a few very niche types, of course. Without further ado, let’s get into it.
Manual Transmissions (MT)
Arguably the oldest and most common transmission for the first few decades of automobile technology, a manual transmission is probably the simplest as well. The transmission has a range of physical gears inside that change the ratio of input speed from the engine to output speed at the wheels – like a multiplier of sorts. This means that the engine doesn’t have to struggle when you want to start off from a dead stop, but also doesn’t have to scream along at high rpm when you’re travelling at speed. A clutch functions as the link between the transmission and the engine, and this clutch needs to be disengaged (separated) by the driver manually when they want to change gears.
Automatic Transmissions (AT)
In a previous article we talked about how best to drive an automatic transmission, but we’ve realized that some still don’t really understand how an automatic transmission works. In principle it is similar to a manual transmission, but instead of a clutch there is something known as a torque converter that allows the automatic transmission to slip so that the engine doesn’t stall when you come to a stop. Think of this torque converter as a rubber band that attaches to the front of a heavy toy car: when you pull the rubber band ahead of the car, it has to stretch and become tense first before the car starts to move. Eventually, car manufacturers added an additional physical lock-up clutch that introduced a physical connection between the transmission and engine so that there would be less of a delay when you press the accelerator once you’re on the move.
Continuously-Variable Transmission (CVT)
This is a transmission that saw popularity on and off over the last two decades but has eventually become quite a staple – especially among Japanese cars. While there are various ways of engineering a CVT, the most common method is two variable sized pulleys. One pulley takes an input from the engine, while the other pulley delivers an output to the wheels. Connecting the two pulleys is a belt, or chain. What’s unique about the CVT is that the size of these pulleys can change in minute steps, which in turn allows the transmission to vary the ratio of input speed to output speed continuously – hence the name Continuously Variable Transmission.
Dual Clutch Transmission (DCT)
Of the various developments in transmission technology, DCT has been the source of both the biggest hits and biggest misses that consumers have ever seen. The technology in principle allows for incredibly fast shift times in addition to being completely computer controlled. As the name suggests, a DCT has two clutches compared to a typical manual transmission. How it works is that alternate gears are split on two different input shafts from the engine – meaning to say a 7-speed DCT will have gears 1, 3, 5, and 7 on one shaft, and 2, 4, 6 on another. While the actual functionality of it is tricky to understand, the main advantage of a DCT is that it can prime the next gear before you need to use it, allowing the transmission to shift quickly and seamlessly if programmed and designed right.
Automated Manual Transmission (AMT)
A little bit of a rare one that has come and gone, the AMT is essentially a manual transmission with a computer controlled clutch and gear selection. You could imagine it as having a manual transmission that’s being shifted by a robot, because mechanically it is identical save for various solenoids and mechatronic units. The AMT has appeared in everything from the Proton Savvy, to various Alfa Romeos, the BMW E46 M3 and E60 M5, as well as the Ferrari 360. In every appearance it has been awful and clunky, and we are glad to have bid farewell to it.
Keyword: DCT, CVT, MT, AT, AMT – What Does It Mean?