Chattering errrr...... Ok now what is it?

[Fox Body]

Is the noise coming from the front or rear of car?

Have you checked the balancer yet? How does the rubber on it look? How does it look when the engine is running? Is it rotating true while looking at it from the side or is it wobbling? I wouldn't think it would be your driveshaft. They don't usually all of a sudden go out of balance.... Could be alot of things. Could be a fan blade missing.... Any more details?

I would be careful about driving the car anywhere until I at least figured out where the sound is coming from, ie, if it seems to be the balancer, park that baby and investigate. Don't drive it.