Unpopular opinion: the 1998 squeaky hub that ate my whole Saturday taught me to quit guessing
A customer brought in a 1998 Trek with a rear hub that squeaked only when pedaling, and I tore the whole thing down three times chasing it. I swapped bearings, repacked with fresh grease, even tried a different cassette, and still got that chirp on the test ride around the block. Turned out the freehub body had a hairline crack that only opened up under load, something I found after about five hours with a flashlight and a magnifying glass. Six bucks for a used freehub and ten minutes of work fixed what a full day of guessing could not. So how do you all chase down noises that only show up under load?