BorgWarner 4473 and 4410 Transfer Cases
Viscous couplings have been used in automotive applications for many years in transfer cases, rear-end differentials, torque converters and radiator cooling fans. Although the concept is not new, the viscous coupling is not well understood in the repair industry and creates a number of diagnostic and repair issues. Part of this problem occurs because all viscous couplings are by necessity sealed units that cannot be inspected. The second part of the problem is a lack of understanding of how they work, principal causes of failure and the proper diagnostic path to follow.