I have an 04 S4 with 60k on it. Everything seems to working perfectly mechanically. However, whenever I go on longer drives - typically 2hrs and cruising at 75/80 for a while - a light vibration grinding starts occuring beneath the clutch somewhere. It does not stop me from driving, accelerating, decelerating, or driving in any particular gear. If completely in nuetral there are no problems/noises. At the bottom of pushing the clutch in you begin to hear the noice again, and then the subsequent vibrations occur as you put it into and accelerate through (slowly of course at this point) each gear. Strange thing is that it will disappear the next day or so and be gone for weeks, seemingly until the next long drive. Is this engine heat related? What component of my clutch or gearbox could it be?? I am afraid to have someone look at it for fear of a typical mechanic's diagnosis of everything under the sun. Any help is appreciated!