It's virtually impossible to overfill the gearbox. It's filled correctly while engine running. If the fill plug is opened when engine is not running over 1 litre of oil will come out.Something worth sharing. My 635d is at 104k miles and last gearbox service was done at 60k by the dealer. I say service. All they did was replace the pan and add 1 litre extra! I am shocked its actually in the invoice !
Anyway went to get the oil replaced at specialist and when they opened the fill hole oil poured out everywhere ! Anyway oil has been changed and gear changes are harsh. I am thinking maybe they put extra oil in to hide this which is very naughty. Anyway I am getting some Lucas Transmission Fix oil additive and going to get the specialist to put some of this in ( worked wonders on previous issue on other cars i.e. power steering on a Aston Martin Vantage and slow engine oil leak on a BMW 730d F01).
Yes, I am sure.Are you sure its filled while engine is running? Did you hear this from another specialist? Certainly over 1 litre of oil came out so maybe it wasnt running. That is terrible. Going back to the 'speciaist' Friday and mention this while they also check the level.