I have a similiar issue with my merecdes also mine blows smoke out the tail pipe and then it will be fine but after a day or 2 my transmission level gets so low that it tough for the car to shift gears correctly i have to get the rpms around 2500-3000 high to even move the car, but when i add more fluid to the transmission the car goes fine until it smokes again then the process is all over again.
Got any ideas what it could be....? bad gasket, or or could be a crack in transmission case...? and how many quarts of fluid are rated for this type of transmission?