Not sure why this happening, as ours is not loud enough to be heard 10 feet away. Could you be missing the rubber mounts between the pump and the surface it is mounted to ? If the pump is mounted directly to the trailer body, with no cushions, it would transfer vibrations to the entire trailer, and could be fairly loud. Just a thought.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.