Hi all, hoping somebody can help me with something I've been searching for an answer too all over the internet & coming up blank; I recently took ownership of a C63 Coupe with the 7-speed 'Speedshift' transmission that is equipped with the wet clutch setup rather than the more traditional torque converter. The transmission has never been serviced so far as I can tell, (not great but not a lot I can do now) so I'm planning to et the fluid & filter changed ASAP. I've watched a few videos and it doesn't look too bad, I have an iCarsoft tool which should ensure I top up to the correct level, however I understand that by just dropping the pan off then refitting & refilling I will only drain ~5 litres of fluid, whilst the total capacity of the system is 7.1 litres.



I know this is all Mercedes would do if I took the car to them, but the fact the car is overdue for this by quite a few thousand miles makes me want to be a bit more thorough if I can be - I have seen videos of people with torque converter equipped cars fully 'flush' the system by removing the oil cooler return line at the gearbox and running the car in short intervals to pump a small amount of fluid out at a time, and topping up with new fluid between each drain (see this video for reference from 12:30 onwards ). From my research I see there is no way to drain the wet clutch like there is the torque converter, does anybody with experience of the job know if doing this will allow me to get out the additional 2 litres or so of oil that otherwise wont drain just by taking the pan off? I know the cooler is thermostatically controlled, but I assume there must be some sort of bypass in the system? I don't really want to do it if it has to be done with the oil at 90+ Celsius, I know that means there will always be at least a few ml in the cooler itself I wont be able to change out but if I can still get a lot more out doing it this way then it would be worthwhile IMO. If not, I'll probably just do another change in a few months time after all the oil has been mixed up again, but I must admit mixing 5 litres of good oil with 2 litres of bad oil just doesn't feel right to me as an engineer.

 

How often does this need to be done? I just bought a 2011 E63 a month ago with 79,000 miles and I’m not sure if it’s ever been done, plan on having it done soon regardless