Automobile transmissions have come a long way since the standard three-speed manuals and two-speed automatics offered since the 1950s. With the debut of the automatic in mass-produced cars, the manual became the base standard transmission. The automatic was a higher priced option. Today, several different types of transmissions are available that give drivers the best of both versions.
Types of Transmissions
In addition to today's six-speed automatic and manual transmission, automakers have developed other types that were originally conceived to transmit power from the engine to the wheels in scooters, farm tractors and Formula 1 race cars. Paddle-shift semi-automatics, which allow the driver to shift gears without a clutch by using thumb paddles on the steering wheel, is one such version.
The Hydramatic 6T70 six-speed automatic transmission was developed in a joint project by General Motors and Ford in 2002. The transmission was designed to keep the mechanics simple and the unit compact with an eye on improving fuel efficiency by 4 percent and overall performance by 8 percent.
The Tremec T56 six-speed transmission powers such performance cars as the Chevrolet Camaro and Corvette and the Ford Mustang, including the Shelby Cobra Mustangs. The T56 was developed using aluminum die cast housing to reduce weight. It features double overdrive and closer ratio steps to minimize time between shifting.
The semi-automatic transmission, also called a clutchless manual, has gained considerable popularity in the last decade. The clutch is electronically operated by synchronizing the timing and required torque and eliminating the need for a clutch pedal. Shifting gears is accomplished by pushing forward or rearward thumb-sized steering-wheel mounted paddles.
The Continuously Variable Transmission, or CVT, can change gears steplessly through an infinite number of gear ratios to provide better fuel efficiency and allow the engine to run at the most efficient revolutions per minute at various speeds. Once used on scooters, the CVT has found its way into Nissan cars. The British- and later Chinese-built MG TF 120 StepSpeed roadster, for example, is equipped with a "Sport" mode, which allows the transmission to shift from automatic to a clutchless manual using CVT.
The DSG, the acronym in German for Direkt-Schalt-Getriebe, is a dual-clutch manual transmission, also called a direct-shift gearbox with full- or semi-automatic abilities. The DSG uses two independent clutches for faster shifting and eliminates the traditional torque converter. Luxury cars, such as the Bentley and Bugatti, use the DSG.
Porsche developed the "manumatic" transmission that combines the automatic and manual elements into a single transmission. The driver is permitted to override the automatic by moving the shift lever to "upshift" and "downshift" positions. In effect, the driver decides the gear shifting instead of the automatic transmission. Like other semi-automatics, some cars are equipped with paddle shifters. An early version of this was the late-1960's Volkswagens semi-autos called "Autostick," an unpopular, but nonetheless pioneering transmission.
- Photo Credit "Shelby GT-H" is Copyrighted by Flickr user: bryce_edwards (Bryce Edwards) under the Creative Commons Attribution license.
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