Civic Si: 6-Speed Manual Transmission
To provide driving enthusiasts with exceptional control and feel, the high-performance Civic Si is available exclusively with a short-throw, close-ratio 6-speed manual transmission. The final drive gear ratio for the 2006 model has been reduced 8.5 percent to maximize the engine's torque for quicker acceleration. By employing multiple large-capacity synchronizers (triple cones on 1st and 2nd gears; double cones on 3rd and 4th gears), the 6-speed offers an exceptionally light effort.

Single cone carbon synchronizers are used on 5th and 6th gears for increased friction capability and reduced shift effort. An extremely short-stroke shift lever provides the quick and precise shift response normally associated with racecar transmissions. Further refining the transmission's sporty, high-quality feel is a short-stroke clutch pedal for quicker shifting, a hydraulic damper integrated with the master cylinder for reduced clutch vibration, and an innovative clutch-friction material for improved clutch engagement feel.

Civic Si: Limited Slip Front Differential
The helical type limited slip differential (LSD) in the Civic Si improves acceleration and cornering performance by insuring that both front wheels receive an optimum level of torque at all times. In a straight line, both wheels are better utilized to put the engine's power to the ground with minimal wheel spin. During hard cornering, the LSD transmits more torque toward the outside wheel to bias more power to the tire with the most grip. This also facilitates the outside wheels longer travel distance relative to the inner wheel. Primary benefits include the ability to accelerate harder exiting corners and enhances the vehicle's responsiveness to throttle inputs in corners. Helical means the differential's gear teeth are cut at an angle to the gear's shaft.

Source: Honda PR