I pulled out the agitator and replaced the drive coupler.
I don't think this was the problem. I pulled off the front panel, so I could watch. Here's what I found:
The shipping rod is missing. Should it be there?
As the machine agitates, the tub is slipping right and left by an inch or two, from the torque of the agitation, causing a noise a bit like a cat howling. The motor is shifting back and forth between the Chassis Rod Brackets.
Just looking at it, it seems that if the shipping rod were there, passing through the Platform and Chassis brackets, it would be providing the support to prevent the shifting.
It almost as if the installer removed the shipping rod, which should have been left in place.
I'm also getting a leak somewhere.
Again, you help here would be greatly appreciated.