it all depends on what your doing with the car: track, daily driving or shady street racing. the more abuse you put on your tranny, the heavier the fluid you need to use. but if your tranny does grind, changing the fluid helps a little bit but its not going to eliminate it. to eliminate it, rebuild then use a reputable fluid and change it often. for fluid i recommend anything but 10/30wt oil, nothing against it but it burns easy.