hey guys. the car is a 6 speed a4 quattro ultrasport. I was driving and everything was fine, when I attempting to drop down in gears, the car would not allow me to put the car into gear. When the car is off, i am able to throw though the gears just fine. but once i start the cars, it wont allow me to put it into gear. I try and there is no grinding, no weird noises, but i can tell that the engine starts to strain. Where the hell is the master cylinder for the clutch anyway? could it be out of fluid? someone please help. I have only had the car for four days and the warranty makes me pay 50%.

thanks guys