Automatic transmissions have taken over as the prime choice for most drivers around the world. Convenience, hassle free shifting, and accessibility have risen above the use of traditional three-pedal shifters. While automatic transmissions started out as simple gear changing mechanisms that were known for less than stellar fuel economy, years of development have catapulted the automatic as the transmission of choice for performance and efficiency.
Quicker gear shifts than manuals have made several manufacturers drop the stick as an option for performance vehicles, relying on the computer and a myriad of sensors to decide optimum points of upshifts and downshifts. Also, smarter computers and sensors have created automatics that prioritize less power and proper gear selection for maximum fuel savings.
On the surface, it may seem that automatic transmissions are limited to just automatic gear selection, but there are many variations that are used in almost all types of vehicles. Let’s take a look at each kind and highlight their characteristics and learn a thing or two about their applications.
Traditional Automatic Transmission
More known as a torque converter automatic, this widely-used automatic transmission can be found in almost every car. This transmission uses a hydraulic fluid coupling or a torque converter to do the job of changing gears instead of a clutch. The ECU (engine control unit) is directly connected to this mechanism to allow smooth and precise engine control of the vehicle.
You may know this a semi-automatic transmission, but it goes by other names. This type of automatic transmission uses a regular clutch and gear configuration, but makes use of sensors, actuators, processors, and pneumatics to simulate manual gear use. These types of vehicles are known for jerky engine performance at low speeds and hard acceleration, but can get high fuel mileage over long distances.
Continuously Variable Transmission (CVT)
Using belts or pulleys instead of traditional steel gears, a continuously variable transmission allows for seamless gear shifting with various ratios dependent on engine speed or RPM. This allows for maximum efficiency and continuous acceleration, which is good for fuel economy. However, engine noise can be loud.
Dual-Clutch Transmission (DCT)
A combination of an automatic and manual transmission, a dual-clutch transmission has no torque converter. Instead, it uses two separate shafts with their own clutches for gear changing, one for odd-numbered gears, and one for even numbered ones. Shifting to higher and lower gears are seamless, but they can get noisy and can shift roughly after wear. The DCT is a dry transmission that does not need the driver to change the gearbox fluid ever. It leaves the clutches dry and wears out its frictional quality eventually.
DSG (Direct Shift Gearbox)
Using a similar setup to a dual-clutch transmission, a direct shift gearbox (DSG) uses two clutches that disengage alternately in changing gears. This setup offers fast shifting and smoother acceleration. Modern systems also provide fuel efficiency that surpass manual gearboxes. A DSG system is a wet transmission, so expect decades of service as long as the fluid is changed regularly.
Usually used in performance or sport oriented vehicles, and also known as “manumatic”, the tiptronic transmission was pioneered by Porsche in the ‘90s. It functions similarly to a manual gearbox, however it uses a torque converter in place of a clutch pedal. There is an option for automatic shifting of gears and an option for the driver to override the automatic mode for manual selection of gears. There is a built-in safety feature that prevents the driver from damaging the gearbox through over-revving when downshifting.