Our local club had a tech session at a local dealer and I replaced the transmission fluid on our 2006 E350. This is what it took to do the job.

Step 0: get the right parts: new filter, 6 liters fluid, 6 new screws for transmission pan, new gasket for pan, new crush washer for drain plug. You also need an E10 socket, a pump for the transmission fluid that can also drain (dealers use a modified Mityvac 7201, ast makes a pump), the special tool to attach to pump (don’t know where the dealer gets theirs, ast makes one that doesn’t look the same but is designed to work with their pump), something like drift number 722589031500, and some way to measure transmission temp (dealers use the computer but I would think an IR thermometer should do it). WIS AP27.00-P-2702W has the detailed instructions.

Make sure car is cool.

Step 1: remove the front 2 plastic panels underneath car.

Step 2: remove exhaust system bracket that blocks transmission pan. Doing this will avoid making a (bigger) mess when you remove the pan.

Step 3: put drain pan under transmission. Remove the drain plug. After fluid slows down/stops, use drift to push the plastic overflow pipe (inside the pan) off, more fluid will come out. After this stops, replace drain plug and remove pan carefully (there will still be fluid in it) and dump remaining fluid.

Step 4: Remove magnet, plastic overflow pipe, and gasket. Clean pan completely.

Step 5: replace gasket, push overflow pipe back where it belongs, and put magnet back in its place.

Step 6: remove filter and replace with new filter. Wipe transmission body where pan gasket will seat.

Step 7: replace pan using new screws. (Note: must replace screws, they are stretch screws.) Torque screws to 4 n-m. After all are torqued, turn each 180 degrees.

Step 8: put fluid in pump and connect to transmission pan drain outlet. Pump some fluid in, a liter or two should do it. Start car. Pump some more fluid in, set pump to allow fluid to drain. After it has drained out, pump some more in and allow excess to drain. After a while, the fluid level will stop dropping in the pump and will increase slightly as the fluid warms up. Watch the temperature. When it gets to 45deg C, pump in about a half liter of fluid, disconnect pump from adapter and stop fluid draining with your thumb, remove the adapter and quickly replace drain plug (trying to lose as little fluid as possible). Torque drain plug to 22 n-m.

Step 9: Turn off car, replace plastic panels, and clean up.