In 4th gear the clutch grinds only at high rpm and all the other gears shift great the gearbox is also making a little bit of noise. I had the transmission looked at and its fine. Do I need to add trans fluid or clutch fluid?
Only add fluid if it is low. It would be helpful to know the year of your Mazda RX8. If the fluid is red, use ATF if it is clear, use gear oil. Manual gear box holds 3.6 quatrs.