【正文】 n be operated either mechanically or hydraulically. The mechanicallyoperated release mechanism consists of a pedal, a return spring, a shaft with lever, a rod m release yoke lever, a release yoke, a release ball bearing with support and a clutch release spring. When the clutch pedal is depressed, the rod and shaft with yoke shift the release bearing and support assembly. The release bearing presses the inner ends of the release levers, the pressure plate is moved away from the driven disk and the clutch is disengaged. To engage the clutch , the pedal is released, the release bearing and support assembly is shifted back by the return spring thus releasing the release levers so that the pressure plate is forced by its springs towards the flywheel to clamp the driven disk and engage the clutch. The clutch hydraulicallyoperated release mechanism consists of a clutch pedal , clutch release spring , a main cylinder , a pneumatic booster, pipelines and hoses and a lever of the clutch release yoke shaft. Time main cylinder acmodates a piston with a cup. The pneumatic booster serves to decrease the pedal force required disengage the clutch. The booster includes two housings with the servo diaphragm clamped in between. The housing acmodates pneumatic, hydraulic and servo plungers. When the clutch pedal is pushed, the fluid pressure from the main cylinder is transmitted through the pipelines and hoses to the hydraulic and servo plungers of the pneumatic booster. The servo arrangement is intended for automatic change of the air pressure in the pneumatic cylinder proportionally to the force applied to the pedal. The plunger moves with the diaphragm, the outlet valve closes and the inlet valve opens thus admitting the pressed air to the pneumatic plunger piston. The forces created by the pneumatic and hydraulic plungers are added together and are applied through the push rod to the release yoke shaft lever。Transmission System A Basic Parts of the transmission system The transmission system applies to the ponents needed to transfer the drive from the engine to the road wheels. The main ponents and their purposes are (1) Clutch to disengage the drive to provide a smooth takeup of the drive (2) Gearbox to increase the torque applied to the driving road wheels to enable the engine to operate within a given range of speed irrespective of the vehicle speed to give reverse motion of the vehicle to provide a neutral position so that the engine can run without moving the vehicle (3) Final drive to turn the drive through 90176。 to reduce the speed of the drive by a set amount to match the engine to the vehicle (4) Differential to allow the inner driving road wheel to rotate slower than the outer wheel when the vehicle is cornering, whilst it ensures that a drive is applied equally to both wheels. B Clutch and Clutch Service In order to transmit the power of the engine to the road wheels of a car, a friction clutch and a changespeed gearbox are normally employed. The former is necessary in order to enable the drive to be taken up gradually and smoothly, while the latter provides different ratios of speed reduction from the engine to the wheels, to suit the particular conditions of running, A clutch performs two tasks: (1) it disengages the engine from the gearbox to allow for gear changing. (2) it is a means for gradually engaging the engine to the driving wheels, when a vehicle is to be moved from rest the clutch must engage a stationary gearbox shaft with the engine。 the lever turns the shaft and the release yoke, thus disengaging the c