One must wonder how much lubrication there is with a tranmission case full of oil and inoperative pumps. The input pinion and bevel gear would be totally immersed going around at a cosiderable rate. Gears have rough edges so it would be like a big high speed food processor inside the gearbox. How much would this activity lubricate the reduction gears and more importantly, how much oil mist for the top bearing? Obviously in a fairly short time the oil would start to overheat but how long is a fairly short time?
The Newfoundland S92 ran out of oil. The Puma Mk2 had a component failure internally, the first for 4 million hours. Both the 225s ditched with no apparant complaint from the gearbox apart from warning lights. All the trials so far have assumed the gearbox to be dry. Have they tried to run one without oil pressure to see what its running time is? It could be a nice surprise, there are enough gearboxs in this world that do not have the luxury of an oil pump.
The biggest problem is working out whether you have lost your oil or your oil pump, that is for somebody else to sort out.