I keep on hearing about locking the rear diff, but I don't know what that means. I know what a differential is, but this "locking" concept is new to me. Can someone explain that to a noob like me? The way my TT-01 is set up now (stock), when you manually rotate one wheel, the other rotates the opposite direction. How would a locked diff work and why is that important for drifting? Also, how can I lock the diff? Is it really necessary to drift?