I believe the advertised figure is around £16000 per hour for a RAF Chinook, though this takes into account the costs of entire infrastructure (cooks to feed pilots etc) and is divided up over flying hours.
Not sure that's what you need. But average fuel burn is roughly 1000-1200Kgs per hour if that helps.
On the subject of gear boxes, I know of an occasion off the coast of Bahrain when the combiner dumped its entire contents in the cabin and ran dry for the 5-10 minutes it took to get over dry land. No damage to gearbox assembly. Boeing do make a robust aircraft!