i have a 91 firebird with a t5.i probably have between 350 and 400 horsepower.the car started out lo3.then i put this 350 in it.well the transmission did fine for a while but now many burnouts later its not.SOMETIMES when im driving and push the clutch in it will start to make this horrible grinding noise.whenever i release the clutch and press the gas again the noise stops.im prepared to have to rebuild the tranny but a buddy of mine seems to think the problem within in the clutch and or throw out bearing.i really hope he is right.does this prpblem sound familliar to anyone?

 

Definitely sounds like a throwout bearing to me. When you push the clutch in, the throwout bearing is pressed against the pressure plate. If it's going bad, this is when you'll hear the noise.

 

Adam
The throw out bearing would make noise everytime you stepped on the clutch pedal.More than likely your pilot bearing is dry.When you drop that trans be sure and check the pilot tip on the inputshaft.Just as you are going down or coming up with the clutch pedal,the motor and trans are not turning the same.Pilot bearing noise will come and go.They seem to act worse when hot.
Scott Brown