Toyota RAV4>> Coupling>> General information
Coupling is located between the engine and the transmission and intended for short-term separation and smooth connection of a bent shaft of the engine and a main shaft of the transmission that is necessary for start-off of the car from the place and for gear shifting without noise and risk of damage of details.

Fig. 8.1. Coupling: 1 – flywheel; 2 – clutch plate; 3 – press disk; 4 – coupling switching off bearing; 5 – the fixing spring; 6 – coupling switching off fork; 7 – a hairpin with a spherical finger; 8 – protective cover

On all models dry one-disk coupling which consists of the conducted and press clutch plates, the central diaphragm spring, a casing and the bearing of switching off of coupling (fig. 8.1) is established .
The conducted clutch plate freely moves on vents of a main shaft of the transmission and is clamped between a flywheel and a press disk by effort which is created by the central diaphragm spring. From two parties of the conducted priklepana disk frictional slips. The conducted clutch plate connects to a nave through details of a quencher of tortional fluctuations. The necessity of a quencher of tortional fluctuations is caused by the following.
At sharp change of speed of the movement of the car, arrival on roughness of the road, sharp inclusion of coupling, and also owing to uneven operation of the engine in transmission of the car there are dynamic loadings causing twisting (untwisting) of shaft of transmission. Unevenness of torque of the engine can cause considerable overloads in transmission owing to emergence of tortional fluctuations and a resonance at coincidence of frequencies, the transferred loadings to frequencies of own fluctuations of transmission. Elastic fluctuations of transmission lead not only to emergence of noise in mechanisms and units, but also to dangerous vibrations, and sometimes and to breakages of details when amplitude of fluctuations reaches big size. The quencher is necessary for absorption of energy of tortional fluctuations.
Coupling switching off drive hydraulic. The bearing of switching off of coupling is installed from the forward party of the transmission on the coupling switching off coupling. The bearing will mix up a coupling switching off fork. When pressing a pedal of coupling the piston in the main cylinder moves and compresses liquid which on a hose comes to the working cylinder of coupling. Under pressure the piston of the working cylinder of coupling, moving, puts a coupling switching off fork in action. The fork of switching off of coupling moves the bearing which influences a spring of a press disk and takes away press a disk from the conducted clutch plate. Coupling is regulated automatically.
Before replacement of components which obviously failed to diagnose malfunction of coupling and its drive execute the following preliminary checks:
Check the level of brake fluid in a tank of the brake system which also serves as the tank for the hydraulic drive of coupling.
If level is lower than demanded, add liquid and check hydraulic system for lack of leak of brake fluid.
During the operation of the engine idling and the gear shifting lever in neutral situation press a pedal of coupling and in several seconds include any transfer, at the same time from the transmission no noise should be heard. If there is an increased noise at transfer inclusion, perhaps, press the disk and/or a clutch plate have defects.
For check of full switching off of coupling launch the engine, tighten the parking brake, press a coupling pedal so that it did not reach a floor on 10–15 mm, and several times switch on and off the first transfer. If transfer joins hardly, check the course of a pusher of the main cylinder of coupling and level of liquid in a tank of the brake system.
Visually check the coupling pedal plug located in the top part of a pedal for lack of an excessive side play and jammings.
From below the car check that the fork of switching off of coupling is established on a hairpin with a spherical finger.