Originally Posted by Remus_Redbone
Throw out bearing is most likely, about 90% chance. Pilot bearing is least likely. Sometimes the throw out bearing will rattle on the trans input shaft when at idle and make a lot of noise when the bearing is actually ok. The fact that it's not making any noise when you push in the clutch supports that. If you start having shifting problems or hear some noise with the clutch depressed, TO bearing may be dying. Requires trans removal to replace, at which time you would want to seriously consider a new clutch & pp.
So right now, if I'm cool with noise and no issues changing gears, I can ignore it and let ride?
After I posted this I drove few more times and noise was there but almost not audible. So it is pretty much quiet again.