Hi Tom,
I was a fleet mechanic for a number of years on trucks and buses. I can't tell you how many times I would see scattered clutches, pressure plates and even flywheels and bell-housings on local school buses. (Remember these were designed on heavy duty truck IH, Ford, GMC etc. chassis to move our children around the neighborhoods) The last one I remember before my area went to Allison Automatics was so bad that parts of the flywheel were stuck up in the dash board above the drivers feet ! I showed her the holes in the floor (noting that she normally wore sandals) and she said "It did make a funny noise"...
I'm guessing your po heard similar noises at a much lower RPM...
By the way, those of us in that shop back then (being younger and somewhat stupider) took both and V8 345 IH and a Ford 331 V8 school bus out to a shopping mall parking lot after hours ( yes, the local constable was even there) and pushed the respective engines all the way up to their governor settings and "double clutched" those New Process tranny's down into granny gear numerous times each and we never even got those clutches hot enough to slip.
The question becomes "how do you get an engine with a governor to explode those clutches and plates etc. driving kids around in 25 mph neighborhoods?"
I'm thinking your po might have the answer to that question
Jim