hi- anyone familiar with these 722.9-G transmissions? - have a 2010 c300 4matic (W204) and changed the trans fluid/torque converter fluid at 40k miles as recommended and replaced with shell 134. The fluid that was drained was pretty much black , did not smell burnt but rather like graphite. Is this normal coloration/smell for this fluid after this timeframe for this tranny? are there lots of graphite parts? I know the this 4matic trans is known for some issues more around the integrated transfer case and related bearing. No metal shavings in the pan, just some fine gray black paste mostly on the magnets.