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Hydraulic pumps can whine , check oil , watch temps and pressure . Run it like you stole it !Also consider is your turbo talking to you or the gears ? I have a mack which has a turbo whine so loud you look for sirens ! Somewhere along the way the wrong oil may have been added . too thin ,So if your scared do a service . My zfs use straight 30 motor oil with spin on filters . Trolling valves may also play into it . My express does not have them . So I can't really comment on those ,I do know that they allow slower speeds ?