Hi all the RC forumer........I need some advice from you that why and how my GT4 2 speed tranny can't shifting when I go for long straight track?? I already try to adjust or loosen the set screw.....try to do it for few time but result also same.....can't shift. Please give some advice..........The 2 speed tranny type are like cam-style and not same as NTC3 or Serpent Impulse. Thanks in advance.