I have a red cat racing volcano and when I have it idling its fine but as soon as I accelerate one of the gears in the gear box seems to slip on the shaft. I just dont know which one? anyone know how to fix this?? All sugestions welcome

What exactly does it do, when you accelerate does it kinda go but not like usual? If so your grub screw on the tranny might have came loose and its running front wheel drive. So when you accelerate it goes but the fronts just spin mostly.