On Sun, 08 Mar 2009 13:28:19 -0700, Bob wrote:

Check the squirrel cage fan coupled to the motor. There could be a
foreign object in there (fell in through the lint screen opening) that
stops rumbling when it sticks to the fan by centrifugal force.

Sorry, I am just now acting on this.

The squirrel cage fan is on the front bottom left, if you're facing
the dryer.

I checked, and the noise is coming from the rear portion of the dryer,
the part closest to the wall.