Found that the area between the filter screen and blower motor was completely blocked with lint after 30 years of use (go figure). Also found that the glide strips supporting the front of the tumbler were warn and the underlying felt pads had shifted out from under the strips, allowing metal to metal contact.
Removed the lint, thoroughly cleaned the inside of the cabinet, replaced the glide strips and felt pads, inspected the motor and rear roller supports, reassembled, and it now works as good as new.
I am very impressed with AppliancePartsPros.com. Their online video was helpful. I ordered the parts needed on Thursday night, they shipped Friday, and showed up at my door at mid Saturday. I was able to do laundry by Saturday afternoon.