Control Trac II
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Control Trac II was a Ford all wheel drive system based on a viscous coupling unit. The viscous coupling replaced the typical center differential used in four-wheel drive applications. The system worked normally in front wheel drive but in addition to the front wheels being driven, a shaft is powered that runs to the viscous coupling in the rear. If the front wheels slip, the viscous coupling progressively releases torque to the rear wheels. Additionally, the Control Trac II system provided a mechanical lock of four-wheel drive though there was no low range provided by the system.
Control Trac II has since been replaced by the "Intelligent 4WD" system, a similar system with the viscous coupling replaced by a computer controlled clutch. The Intelligent 4WD system functionally acts similar to the Control Trac II system, with the front wheels being driven predominately with torque being sent to the rear wheels only as conditions dictate. The Intelligent 4WD system also lacks the mechanical lock provided by Control Trac II.
