On a separate note though, why would you want to drain the gearbox oil - it is filled for life, unless exceptional circumstances occur, which may merit a top up. It's not a commodity that should be changed ordinarily, unlike the engine oil.
Mike
The A2 gearbox has a breather which allows air movement inside the box.Isn't the gearbox a sealed unit? If such is the case, how can humidity enter and create problems?