A yaw control system for an automotive drivetrain includes an equal torque differential, an engine-driven hydraulic pump, and hydraulically actuated control brakes operable to apply a resistive torque to either a left or right axle of the driven wheels. An acceleration-responsive control valve actuates one of the control brakes according to the direction of lateral acceleration of the vehicle. The control valve includes an inertial or seismic mass that moves a valve member to connect or disconnect the control brakes from the hydraulic pump. The control brakes are attached to the vehicle chassis so the resistive torque is reacted through the chassis, thereby inducing a yaw moment that coincides with and assists the turning of the vehicle.