The car is a 96 pontiac grand prix. The noise only happens when I am moving forward and only when I push on the gas. It does it in drive, over drive, 1st and 2nd. It does not do it when I am in reverse, neutral or park. I can push the gas all day in park and never hear a thing but as soon as I push on the gas to accelerate forward I hear the noise. If I am driving and I take my foot off of the gas it stops. Also I don't hear it once I hit a continuous speed of about 45 or so. That is unless I press the gas to go faster. If I just hold a speed I don't hear it. It seems like the only time I hear it is when the car has to work in order to move forward. If that makes any sense.