Not the clutch, but the resulting speed of the fan is louder. In the way that a desk fan moving from low, to med or high gets louder. As compared to my worn OE clutch and my brothers D1 with a different clutch, the 2991 is louder. Standing outside the truck while it's idling or from the seat while driving.Why would the clutch be noisy? I can see another fan design being loud, but the clutch?
|Q. What is the difference between a standard, heavy and severe duty fan clutch?|
|A. Each fan clutch type is designed to simulate the performance of the original equipment clutch that it replaces. All fan clutches are for specific applications and should be applied only on the application for which they are cataloged.|
Standard Duty Thermal
Turns the fan 50-60% of shaft speed when engaged. Used with fans with lighter pitch. (1-1/2" of pitch) Flat plate impeller design with 30 Sq. In. of working surface.
Turns the fan 80-90% of the shaft speed when engaged for increased cooling. Used with deeper pitch fans. (2 1/2" of pitch). Land and groove design with 47 Sq. In. of working area allows higher operating RPM's.
Severe Duty Thermal
Turns the fan 80-90% of the shaft speed when engaged. Used with deeper pitch fans. (2- 1/2" of pitch). Land and groove design with 65 Sq. In. of working area. Larger working surface provides cooler running and longer life expectancy.