What is the tapping/rattling noise?

i have a 95 buick lesabre. i have taken this vehicle to 3 mechanics: the first one narrowed it down to the transmission. the second one said the flywheel. The orignial owner's mechanic said it was from the pump in the transmission and it wouldn't hurt anything. i am a female and i do not want to ride in a noisy vehicle. Some with experience or knowledge of this, please help me.