Clutchless manual transmission is a system which uses electronic sensors, processors and actuators to change gears as and when decided by the driver. There is no need to depress a clutch pedal before making a gear change. Instead, the driver changes gears with a gear-shift lever.

The driver only has to continue placing pressure on the lever while he selects a gear, without the tricky bit that means having to find the “biting point” at which to disengage the clutch in a manual car.  In a semi-automatic, the pressure placed on the gear lever trips a switch, engaging a hydraulic clutch actuator.

Hall effect sensors gauge the direction of requested shift. This input, together with a sensor in the gearbox which senses the current speed and gear selected, feeds into a central processing unit. This unit then determines the optimal timing and torque required for smooth clutch engagement.

To stop the car, the driver only needs to apply the brake, moving the selector into neutral. In every action, the gear selection movements in manual and semi-automatic cars are identical, except for clutch actuation.

In this way, semi automatic cars avoid torque converters, which must be used in automatic cars. The fully hydraulic nature of a torque converter provides smooth starts and shifts, but with the price of higher fuel consumption for keeping the flywheel rotating.  Semi-automatic cars therefore consume less petrol than automatic cars