GMC Savana

I have a 2000 GMC Savana 1500 Conversion Van, It's a 4.3 V6 automatic with 95,000 miles. The problem is the drivebelt is squealing. It squeals when it is idleing, and gets louder and faster when I accelerate. There is nothing leaking, and so far I have replaced the belt, the tensioner pulley(entire assembly), and the idler pulley. After all this I am drawing a blank. I am desperate to stop the annoying sound PLEASE!
November 22, 2007.

Remove the belt and check the pulleys, make sure they are clean and turn easily, check for side play {whiggle them} to see if any are going bad. Check all pulleys including water pump pulley. Have seen a loose pulley make a belt slid causing it to squeel. Look at the pulleys to see if they line up properly.

Nov 22, 2007.