makes a grinding or scraping noise?

1997 Buick LreSabre makes a grinding or scraping noise when going forward but not while idling or gunning the motor also not when going in reverse. After using the car early in the day there seemed to be no problem . Later in the day I started the car in the afternoon and it started normally. When I put the car in forward gear and started moving there was a grinding or scraping sound coming from the front right side under the hood. When I stopped and gunned the motor it sounded fine. Going in reverse also sounded okay but each time in forward drive the noise started again. Any ideas?