Well, when the clutch is engaged, the pilot bearing isn't rotating at all because both rotating parts (crank and trans input shaft) are going at the same speed. So if that was the problem, it should only make a noise when the clutch is disengaged.

Could be a throwout bearing, and that's the most common one to start failing. That's the easiest one to inspect and replace though. Usually the bearing will whine when there isn't any load on it, so when there is enough load on the bearing it tends to quiet down. That sounds like your problem if I'm hearing you correctly..


Could also be the transmission input shaft bearing, but I'd check that last because it's the least likely to have problems.