I used to drive a p10 gasser, not sure if it was a workhorse, but it had extremely loud brakes! I complained a few times and was told the same things grc88 is stating. Gave me fits with headaches and ear pain. Took it to the safety committee and nothing came of it, then for reasons dealing with "fleet consolidation", the truck was sent away to another center so more of them could be in one place to facilitate repairs, I was told. I now have a p10 diesel that aside from being a 5 speed stick, is as quiet as an old p5.
That said, I would probably have gone the osha route by now if I still had to drive that ol turd.