Whining noise was coming from under the hood of a 05 Trailblazer and Ranger GM of Hibbing Minnesota said the alternator needed to be replaced. It would cost $462.17 plus $80.00 for labor. I told them I'd wait to have it replaced. I brought it to a different garage and he diagnosed it as a bad tensioner pulley. Costs $51.00 with the part plus labor. He also said Trailblazer's are known for having these go bad. Shouldn't the dealer have already known this? They must see this problem a lot more than a small garage would. Guess their hurting for business so decide to try and con innocent customers.