Abstract: A viscous clutch head may be replaced by selecting a viscous clutch head and a mount adapter. The viscous clutch head and the mount adapter may be selected from a group of universal modular fan drives and from a group of mount adapters. The mount adapter of a threaded type or a flange and bolt type may be selected. Depending on the viscous clutch head to be replaced, a fan adapter and/or a pilot adapter may also be selected from a group of fan adapters and from a group of pilot adapters. Accordingly, a range of models of viscous fan clutch systems may be replaced by using a limited number of parts. These parts may be stored on a tool cart. As different models of viscous fan clutch systems may be replaced using a limited number of parts, the in-stock inventory of replacement parts may be reduced.

Abstract: Some embodiments of a clutch system may drive an output portion to rotate at a first rotational speed when the clutch surfaces are engaged and to rotate at a second rotational speed when the clutch surfaces are shifted to a disengaged position. The viscous two-speed clutch system may employ a viscous drive system that causes the output portion to rotate even when the clutch surfaces are disengaged. In such circumstances, the cooling fan can be driven to rotate at a first rotation speed due to interconnection with a drive source and to rotate at a second rotational speed even when the clutch surfaces are disengaged. Thus, the clutch system facilitates the flow of cooling air both when the vehicle cooling system activates the fan (e.g. by causing the clutch surface to engage) and when the vehicle cooling system deactivates the fan (e.g. by causing the clutch surfaces to disengage).

Abstract: Some embodiments of a fan clutch system may drive an output member to rotate at a first speed when opposing friction clutch surfaces are engaged and to rotate at a second, slower speed when the friction clutch surfaces are shifted to a disengaged position. In particular embodiments, the multi-speed clutch system may employ an eddy current drive system that is arranged axially rearward of the friction clutch surfaces while the fan blade device is mounted in a position that is axially forward of the of the friction clutch surfaces.