How a World Rally Car's Enormously Complex Center Differential Works (2024)

Differentials are pretty easy to understand once you know how they work. Torque is distributed from a driveshaft and split to the driven wheels, transferring energy to the road. But when it comes to top-level rally car differentials, it gets a whole lot more complicated.

Because modern WRC cars are all-wheel drive, they have a center differential that splits torque from the engine to the front and the rear. Simple enough, right? Well, there's a little more to it than that.

You see, in order to get through a corner fastest, drivers need a varying amount of lock between the front and rear differentials, which means the center diff is constantly locking and unlocking depending on how much throttle and steering angle the driver is applying.

For example, if a driver has the wheel pointed straight and their foot to the floor, the onboard computer determines they need as much traction as possible, so it fully locks the center diff. But if a driver is turning and braking into a corner, an opened differential will provide less understeer. As the driver transitions from entry to exit, the diff will unlock then lock back up as inputs change. It's incredibly complex and extremely clever.