The above post describes the use of a locked differential, which does exactly as you described. However, a one-way differential is a differential for the front of the car which allows the front wheels to free-wheel under de-acceleration or braking conditions. This makes the car act like a 4wd car under acceleration, but a 2wd car when you let off the throttle or hit the brake. It's a lot easier to get the car to break traction or control the slide with a one-way. Hope that helped!

By the way, this is my first post on rcuniverse and hopefully not the last! [8D]