What could be causing a loud scraping noise in back of vehicle. Only happens whe on 2009 Kia Sportage

Started sounding like a whistling noise first. Now sounds like metal scraping. Under warranty. Had a KIA dealer look at it- I thought it was wheel bearing. They say they can't find anything the matter. They sugggest I put on new tires- which I did. Sound was still there last night

Asked by for the 2009 Kia Sportage
how are the rear brakes or backing plates
Just had it inspected yesterday - they took off back wheels and said brakes are ok
1 more answer
Get a paid diagnosis from an independent shop and if they find that the noise is caused by an item that should be warranty , then ,if your confident that the dealer will fix it properly under warranty , bring it back to them with the diagnosis print-out(have a copy for your own records) and make sure the issue is documented properly at the dealer ---check your receipt from them before signing it!
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