View single post by Lane Shirey
 Posted: Mon Jun 11th, 2018 10:52 am
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Lane Shirey

Joined: Wed Apr 30th, 2014
Location: Downingtown, Pennsylvania USA
If it turns out not to be bearings and it is coming from the gearbox, I have a theory. 

I’ve had many fans that I’ve restored that the gearboxes were silent and then I cleaned them and added new grease and they became noisy. 

This is my theory. They’ve been run so long without grease or insufficient grease, that the gears have seated and developed wear patterns based on that geometry . When you add grease, it changes the tolerances and causes the gears to ride on a little different contact area. I feel that this causes the noise. Most get quiet eventually, I suppose when the gears reseat with the new geometry. 

Also since you’ve replaced gearbox bushings, it may have caused a geometry change.