1999 powerstroke clutch noise
 

I have a 1999 f-350 power stroke 4x4. The clutch does not slip at all but when I am winding the gears out say pulling a heavy load or just getting up to speed the clutch pedal stays on the floor when I push it to change gears. Also when I get up to high rpms it sounds like something is knocking in the clutch like a bad bearing but if I put just a slight bit of pressure on the clutch pedal it quiets down. It will also knock when idling in neutral but again if I put slight pressure on clutch pedal it goes away. My question is do I need to replace clutch? Every other vehicle I've had that the clutch was bad in they would slip. Thanks