Clutch plate slips when it wears out..there are two disks one on engine and one on gear box, they become apart when you press clutch to easily change the gear and disconnect gears at idle, they are pressed against each other by force and the rotate together when the clutch is released and car moves.
When they slip you cannot put in the gear and/or you keep giving race the engine hardly moves the vehicle. In local terms (engine zorr nai laga pata tyres pe) ya engine gear ni khenchh pata...lolz...hope the exp helps or you get a better one
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