I had one of those kyosho plastic blocks inside the front diff, which is should have mind you. But after a while they get worn out and what happens is that you only get drive to one of the front wheels and that caused my car to pull one way when accelerating and braking. Just replace the block or do what I did and put the gears inside and make it a proper diff.
Bayside - http://www.wynnumrc.org.au
Kyosho V One RRR Evo
Novarossi Plus 12-3SCT