Funny sound from throw out bearing

[Hotelbldr]

Does anyone know what happens to a throw out bearing as it wears out. Does the clutch respond differently? Mine is making a sound once in a while that goes zzziiiitttthh. Mostly when it's cold. Any takers on a answer to this one?

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66 burgandy convertible; 306 (289 bored .03 and 302 crank) edelbrock: Performer intake,4v carb; hurst 4 spd; 2.8:1 rear;