Steering System Noise Definitions: Shudder
WARNING: This page is about a different car, the 2006 Mercury Milan, 2006 Lincoln Zephyr, and 2006 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
Shudder is a low frequency (10-20 Hz) oscillation of the entire steering system (tires, wheels, steering gear and linkage, etc.) when the vehicle is steered during static park or at low speeds. Shudder is very dependent on road surface.