The patient is a Whirlpool top loader, circa 1989. I've had no problems with it in the past; it has been a solid performer.
Recently the agitation is clearly reduced from its normal behavior. The normal setting will agitate the clothes, but less vigorously than before. The delicate setting barely jostles the clothing. And I don't know about the permapress setting; I never use it.
While it is agitating a load, I can easily twist the center post with the agitation vanes in either direction with minimal resistance.
A little bit of internet investigation leads to discussions of the "dawgs". (Gotta love yet another instance of colorful terminology in washer lingo!) But before I start tearing into the machine, it certainly can't hurt to ask the experts here if that's a likely failure point, or whether I should start with a different assumption.
Thanks for any advice.
Art