My Whirlpool Duet Sport front-loading washer (Model WFW8300SW02; about 10 years old) makes noise during the spin cycle. Most of the time it is a low buzz, but at the fastest part of the cycle it’s very loud and sounds like a circular saw cutting wood.

It happens whether or not there are clothes or water in it.
It happens whether or not the washer is jumping and shaking.
I took off the back cover and looked at the belt; the belt seems OK.
It doesn’t seem to be related to the drain pump.
As far as I can tell, the bearings are OK – at least the basket doesn’t seem to be loose or move easily.
I haven’t been able to see anything stuck between the tub and the basket – although I could have missed something.

Any suggestions? Thanks.