Started out as a loud ticking or knocking noise, which i noticed while parked with my foot on the brake in drive. Got louder with time. You could only here it while stopped or as it got worse while driving slow after it got to second gear you couldn't here it. I was very lucky that Chevy covered it under warranty even though it was out of warranty by a year and a half. I think because the miles were so low. Had they not covered it i would been pissed as it has such low mileage and i drive it very nice.