Suburban 3/4 Ton 4WD V8-305 5.0L (1986)
than a standard fan. These benefits are possible through the addition of a thermostatic clutch to the fan drive.
When the engine is cool, the clutch allows the fan to "slip" or turn at a speed slower than the engine. By turning at a slower speed, the fan uses less
horsepower, which saves fuel, and is quieter. When the engine temperature reaches a preset temperature, the fan "engages" and turns at the same speed as
the engine.
"Engagement" of the fan provides increased airflow through the radiator to cool the engine. As the airflow increases, fan operation becomes clearly
audible. This increase in noise can easily be mistaken for an increase in engine RPM and may be incorrectly blamed on the automatic transmission.
When operating an unloaded vehicle in cooler ambient temperatures, the thermostatic clutch usually won't engage. However, if the vehicle is pulling a
trailer, heavily loaded, or operated at high ambient temperatures, the thermostatic clutch may cycle on and off as the engine temperature rises and falls.
The sound of fan operation under the conditions described above is a sign that the cooling system on your vehicle is working correctly. Replacement or
modification of cooling system or transmission parts will not change or reduce the noise level. Attempts to reduce this noise will only give you, the
customer, a false sense of vehicle unreliability and the inconvenience of having your vehicle out of service.
