Hi Tim,
I was working on a 1989 kenmore washer today and had a similiar issue. It is gross to find what causes this or maybe a long cycle w/o enough soap to hold the dirt causes the problem. The first issue was a 20 year accumulation of soap, dirt and oil plus the years turn it black on top and very oily.After one use everyone hates washer magic for not instantly curing the years of build up. It is not your fault, you don't see it and no one has told you,.. till now. This stuff will reside in the back bottom of your maytag and be 2 inches thick, ohh yeh. A good cleaner will take strategy and months of preventive work to reverse the build up. Like your veins good meds will take a while to work or if youre me I would pull the boot spring, front panel and remove the front of the tub and hose it out.

Post a not if I am wrong or give more info an I am glad to help.