Most modern cars come with an automatic gearbox, and manuals are a dying breed, as the saying goes. That said, with automatic gearboxes itself, you would have heard of different terms such as AMT, iMT, CVT, torque converters, and DCT. But what are they and how do they differ? Here are the types of automatic gearboxes decoded for you.
AMT
An Automated Manual Transmission, or AMT is the most common type of gearbox. An AMT gearbox is essentially a manual, where a hydraulic actuator system and an electronic control unit engage and disengage the clutch instead of the driver doing so. A car with an AMT gearbox does not have a physical clutch lever and the gearbox also has a manual mode where the driver can choose to go up or down the gears.
iMT
An Intelligent Manual Transmission or iMT is similar to an AMT, however, the biggest difference is the traditional H-pattern gearshifts and the driver has to shift the gears manually, just without depressing the clutch lever. An iMT gearbox uses something called an ‘intention sensor’ on the gear lever, which sends a signal to the Transmission Control Unit (TCU) to make the change when the gear is shifted by the driver.
CVT
A CVT gearbox, or a Continuously Variable Transmission is unique and is found on scooters. However, the CVT tech is also popular on cars such as Honda, Kia, and a few others. A CVT uses two cone-shaped pulleys connected by a belt. One of the pulleys is connected to the engine and the other to the wheels and as engine rpm increases, the belt on the pulleys moves accordingly to maintain the tension, giving them infinite gear ratios. A CVT gearbox is also compact and easy to construct, which makes them popular, especially with scooters.
Torque Converter
A Torque Converter (TC) is the traditional, actual automatic gearbox, which has been in use for many years. The gearbox will self-change gears on the move and uses a complex hydraulic system and planetary gears to do all the shifting, which makes it ideal for powerful engines. A allows a lot of torque transfer at low RPMs, making it an ideal choice for most top-end cars.
DCT
A Dual Clutch Transmission (DCT) is gaining popularity in India, especially with Volkswagen, Skoda, Hyundai, and Kia. As the name suggests, a DCT uses two clutches, one for selecting 1st, 3rd, and 5th gears, while the other clutch is for selecting 2nd, 4th, and 6th gears. It works on similar lines as an AMT, but the DCT keeps the next gear engaged, so the shifts are faster and seamless. A DCT allows manual shifting as well, giving the driver more control.