Thanks very much Gordon. I’ve done a bit of research and I wonder if you can clarify a few of the things associated with doing the transmission fluid change? How exactly does the adaptor kit work, and what else is involved?
Gordon then came back to me and I can give a short summary of the process, for those who might wish to avoid the not insignificant expense (£300 plus) of having the fluid change performed by a dealer or Mercedes-Benz specialist at the required 30,000 mile intervals.
Basically, there is no dipstick in the Mercedes-Benz 7G-Tronic transmission fluid pan, and the correct fluid level is achieved when performing a fluid change using a level pipe and the above mentioned adapter. After removing the drain plug and draining off the fluid by removing the level control pipe, you then remove the pan itself, clean it, replace the filter, and clean the magnet used to trap any swarf. You then refit the adapter and level control pipe into the pan and then refit the pan, with a new gasket and new bolts. The correct refill level is achieved by fitting the necessary adaptor into the drain plug, which is effectively a filling and overflow device. When the fluid level is slightly overfilled, as intended, any surplus fluid is then drained off through the adaptor, like any fluid overflowing a weir. You then allow things to settle and, with the car on level ground, and raise the fluid to 40 degrees Celsius temperature, achieved by running the car and then allowing it to cool down, which may take some hours (measure with a suitable thermometer), and then allow any further surplus fluid (it will have expanded with the elevated temperature) to overflow, before removing the adapter, putting things all back together, and then following up with a road test. There are around 14 steps in the process, as described by Gordon, so space precludes publishing a full description here, but I would be happy to e-mail this to any readers who would like the step-by-step details. Draining down of the torque converter, which has a separate drain plug, is part of the official fluid change, but Gordon says he has been advised that this is not really necessary, and we’ll take his word for this. Thanks to Gordon for the money-saving advice for fairly advanced and confident DIY readers. To this I might just add that I found that a full kit of transmission fluid, pan gasket, filter, new magnet and pan bolts is available from an accredited Mercedes-Benz dealer on e-bay for just £115, which surely must be a big saving on over-the-counter prices.