i have a 99 tahoe with a 5.7, recently i've been getting a scraping/grinding sound when i'm slowing down. i think it's when it's down shifting. it sounds like the brakes are worn down but the're fine. i dont have to be breaking, it will still do it when i just take my foot of the gas. it's not to bad when it's warm but when it's cold it sounds horrible. it never happens when i'm accelerating.... any help please!! thank you