Ive got a trueno ae101 and when in first gear sometimes and reverse most times, there is a grinding noise when releasing the clutch (about 3/4 of the way out). It sounds like its not in gear but its not as loud as that, but has a whyning grinding sound.
2nd 3rd 4th 5th etc are great, no slips.
Only seems to happen when the car has been driven, then parked for 20mins or so and go to reverse out of a park and i get the sound. Once the clutch is right out its fine, its just when riding it, it makes this sound.