Tc02c Newbie unsure where to start

[Kev132]

so basicly, i purchased a 2nd hand tc02 and its been great, we've just come indoor and it was ok but a little tail happy, so i put some new mini pins on the rear and it was great, however when accelerating from standing or low speed the car makes like a grinding noise as if the gears are all mashing together, ive pulled the gearbox apart and all the gear look great, should i next be looking at the diff or the slipper ?

thanks in advance, having never owned a buggy and not building this one either, im kind of stabbing in the dark at what it is