of belts or other coupling devices such as a timing chain key features of the present invention include a wet friction fan drive system with a unique fan speed sensor a unique hydraulic valve design that enables electrical signals from the fan speed sensor to pass through the center of the valve body and a unique lubrication system used to cool the fan drive assembly the lubrication system passes lubrication oil concentrically around the housing of the valve body in accordance with a preferred embodiment of the invention the valve design is independent of the clutch shaft subassembly and can be used in an infinite number of permutations of the base shaft design the basic operation of the wet friction clutch is described in u s pat nos 7 047 911 7 249 664 and 7 178 656 the disclosure of which are hereby incorporated herein by reference in general as shown in fig2 the housing member 12 includes a body member 30 and a cover member 32 which are securely affixed together such as by bolts 33 or other fasteners the body member 30 is also securely affixed to the input pulley 16 such as by fasteners 34 and both rotate at the same speed.