Gearbox Fluid

[newboost]

Does anyone know what type of fluid I should be using in my gearbox (r33 s2 gtst auto). Valvoline, Castrol, Other types. What are the differences between the brands both good and bad. I have had the car for 2 years now and have noticed that it seems to be getting longer in the changes. I have been told that if I change the fluids it should help out.

Is there additives that I should put in at the time when I change it all. (slick 50,Nulon auto treatment, others brands)

Any help with this would really help me out with this.