Hot take: the guy at the shop in Red Deer was right about my chain slack
He grabbed my chain at the rear sprocket, wiggled it, and said "that's a chain that's gonna eat your case." Two weeks later I'm running 30mm of slack per the manual instead of the 15mm I'd been doing for 3 seasons, and the whine I thought was my transmission is just gone. Anyone else get humbled by a spec they'd been ignoring on their own bike?