i too have a S40 installed in my d15b...first gear cuts-off at 95km/h and second gear cut-off comes at 135Km/h but mine is super long gears, and the Rpm goes too slow.. are you sure its short ratio bcoz by my experience S40 is long ratio and s20 is the short one..now i am going to put a short ratio gear in it, but i am confused...