My partner has a mk4 golf gti when he changes gear the gears grind slightly. When sat in traffic he puts the clutch right in (flat to the floor) and in 1st gear, even with the clutch flat to the floor the car shakes where you can feel the clutch starting to bite. When he takes the car out of gear the shaking stops. Reverse always grinds. He has changed the master cylinder and the fluid. Does anyone have any idea what it could be the car runs fine apart from this problem????