Volvo MD 11C , gearbox and Walter V drive. The oil level in the V drive rises and drops in the gearbox. Leaking seal is perhaps too simple, I noticed some air escaping from the gearbox when checking the level just after running the engine. Is there a hidden air valve in the gear box wich is closed now? When the pressure doesn't rise , I assume the "leaking seal" between the gearbox and the V drive is no longer doing so. Any suggestions would be very welcome.