Problem with my 1998 Grand Prix

Can anyone help me with this problem? My car is making a ratteling noise underneath(about the middle of the car) between 1,500RPMs & 2000RPMs and then stops. I have 153,000 miles on it and it runs great. My concern is the transmission. The car shifts fine through the gears and the ride is smooth. However I would like to fix this before it becomes a large problem. Thanks of the help.

Have you jacked the car up to check it out? You might have a heat shield that's come loose or something.

My car is making a ratteling noise underneath(about the middle of the car) My concern is the transmission.

It wount be your tranny,since the noise in coming from the middle of the car.The tranny sits on the front drivers side of the car under the hood.I agree with cass,either a heat shield or exhaust rattle.Id take it buy an exhaust shop and have them take a look.

~Larry~