This type of transmission is known as hybrid between a fully automatic and manual transmission. It is also called automatic manual or clutchless manual. This transmission system work with a shifter of paddles just like manual transmission. Paddles are located behind the steering wheel. Gears automatically shift by the use of processors, actuator, pneumatics and sensors. It shift when it signalled the changes. However, the clutch pedal don’t need to operate in this transmission system.

Semi-automatic transmission has been use on heavy commercial vehicles for many year because of it mechanical function of the gears. The latest provide are lightening-fast, which is almost undetectable gearshifts. This type of transmission rely on microprocessors which is to control the mechanical gear ratios by the use of electrical operated actuators and servos. Due to the high cost of semi-automatic transmission system, they were limited to high-end supercars at first, but these days increasing number of manufacturers are fitting them to mid-range cars.

The dual clutch systems has two clutches, one of it is controlling the gearshifts in the even numbered gears, and the other controls the odd numbered gears and reverse. However, this arrangement does not disturb the power flow from the engine. In some cases the driver still need to initiate a gearshift or paddles, but there is no need for the driver to operate the clutch.

Automatic clutch cross section with gearbox.


  • The driver experience smooth shifting
  • No energy losses due to slippage in torque converters, or during the time lag of manual shifts


  • They are complex
  • They are more expensive to maintain and repair than manual transmission
  • Unsatisfactory performance due to variety of possible issues.
  • Semi-automatic transmission are prone to failures.