I think you will find the the drum has failed. If you remove the top (2 screws) after switching off and unplugging from the mains, then slowly turn the drum by hand you will notice the rear of the drum casing is all cracked and split, esp. the lip where the rubber guide wheels run(see at the base of the dryer where the belt tensioner/jockey assembly is mounted.) What you are hearing is these wheels slowly destroying what is left of the drum casing. Skip case I'm afraid (unless its still under warranty) ... Whirlpool dont want to know ... huh, they are no better than Philips were... cheap cr*p. Sorry :O(
Truckbusuk, March 2006