1987 Buick Park Avenue Scraping noise in 1st and 2nd gears,

My 1987 Buick Park Avenue makes a barely audible scraping/scratching noise when the transmission is in either the 1st or 2nd gear. But as soon as it gets up to Drive (3rd) or overdrive, the noise disappears. It makes this noise whether you are accelerating and it is shifting up, or you are decelerating and it is down shifting. It seems to get slightly quieter when you let off the gas, but not much.
And the noise does not change when turning a corner. Please help! Thanks...