2001 Hyundai Tiburon has been making a faint grinding noise when taking foot off gas. You can hear it going 10 mph then more as you go faster. Yu cant hear it when on neutral

SOURCE: Transmition grinding when i go fast then either go into neutral or take foot off gas

Sounds like the trans imput shaft bearing. They tend to wear and cause shifting problems. It also could be synchronizers. Marlin Crawler makes aftermarket trans bearings for these transmisions.
www.marlincrawler.com
I hope this helps. Also check tranny fluid and clutch. a worn or bad clutch will also cause this.