Unscrewing the oil drain plug from the rear final drive
1. Drive the vehicle a sufficient distance to warm up the rear final drive to normal operating temperature.
2. Place the vehicle in a horizontal position over the inspection pit.
3. Wipe the area around the fill/level plug in the rear final drive located on the left side and unscrew the plug.
4. Place a suitable container under the drain plug located on the right side of the rear final drive housing and unscrew the plug (see picture).
5. Drain the oil into a container. Clean the plugs and remove any metal particles from the magnets attached to the plugs.
Article text obtained from the website (MercedesMan)
6. After draining the oil, clean the drain plug threads and reinstall the drain plug, tightening it to the specified torque.
7. Fill the rear final drive with the exact amount of oil required and check the oil level. If the exact amount of oil is filled and the oil level is above the norm, install the oil level check plug and make a short drive to distribute the oil between all elements of the rear final drive. Recheck the oil level and, if necessary, bring it up to the norm.