My CEL was coming on intermittingly so I took my car in for and oil change and a diagnostic.I had a bad motor mount an bad cats in which they replaced today but now they tell me I have a bad transfer case. I have this humming noise coming from the wheels that gets louder and faster with speed. I thought it was just the aggressive design tires that were making that sound but the dealer says it's the transfer case and they will need a solid week to repair it. So far my STS has been back to the dealer 24x.