from what I have heard it eliminates having to deceide what viscosity fliud to run in your diff, it acts like limited slip differential in a full size car and it uses grease. depending on what is needed more traction or less it detects this and applies. It is a drop in upgrade, you might want to open it up and check the amount of grease to see if they have enough before installing. Replacing the front diff makes the biggest improvement than the center, there is no need to replace the rear. The losi is a similar design to the Fiorini for a lot less money the Fiorinis go for about $250 a piece