speed t spur gear stuck on

[lo$i swagg]

i recently purchased a losi speed t roller and added the mamba max esc with valineon fan and cm36 9000kv motor i wanted to lower the tooth of my spur gear but its like its fused on the thing. tried to pop it off but it will not budge any help would be grrreeaatly appreciated im new to the rc thing started like two months ago with the new cheap electrix stadium truck but i upgraded that to all rustler xl5 waterproof setup from cambers to traxxas servo i now have the sidewinder 5700kv setup in it its fast but not a losi i really wont buy anything else ever go losi lol