Have a 2011 S-750 with only 350 hours on it and started losing hyd oil. Had it over at another farm using it couldn't see any oil on ground. Keep adding a little oil know and again. Added about 5 gallon in 100 hours. Finally got it home in the shop. Lifted cab nothing leaking to the outside. Checked the chain case sure enough the oil had went in there. Know how do I decide which motor is putting the oil in the chain case. This machine has been a pain in the rear since it was new and now this. Probably time to send it down the road.
Tough to do with that min. amount of leakage per hr (quart every 5 hrs.?), but you could put all four corners up on stands, take the chain case inspection cover off, mark your oil level, and for several hours run one side of the machine (weight in seat, string on controls). Might find out both sides are leaking....worse case.
it's not the motors leaking.. its the gearbox seals. typically if one side is leaking, the other side will be soon. :drinkup