Old timer told me to chase the squeak, not the part
Back in 2003 I was working at a shop in Tucson and this retired racer named Ray kept bringing in this bike with a creak that only happened under hard pedaling. I swapped the bottom bracket, then the crank arms, then the pedals, everything torqued to spec and it still made noise. Ray finally watched me chase it for an hour and said 'it's the seatpost, kid, I can hear it in the frame.' I laughed because the seatpost looked fine and I had greased it the week before. Turned out there was a hairline crack hidden under the clamp area, just barely flexing with each stroke. He was right, and I spent about $80 in parts I didn't need before listening. Has anyone else had a stubborn noise that turned out to be something totally obvious once you stopped assuming it was the drivetrain?
Had the same thing with a creak that only showed up when I stood on the pedals. Tore apart the whole crank, new chainring bolts, greased everything twice, still there. Turned out the noise was the rear skewer, the cam was just barely worn so it moved a hair under load. Swapped it for a spare and the creak vanished. I felt like an idiot after two weekends of work for a five dollar part. Now I check the cheap stuff first before I touch the drivetrain.