I just changed fluid in my front differential without removing the shaft nor other parts. It is time consumed and a little messy but if you have a small pump and wear gloves then it is very quick and easy. Attached is a picture of stuffs I used, a 3/8 OD(outside Diameter)clear hose, 3/8 hose x 1/4 NPT fittings re-tapped to 12mm x 1.50, a bicycle pump, a small funnel and a tie-wrap.
Steps:
1- Drain old oil and measure the amount collected.
2- Screw in the 10x1.5 fitting and plug in the hose, just hand tight
3- Route the other end of hose to upper area for gravity feed.
4- Attach the funnel to the hose fitting with tape and secure it to something.
5- Pour new oil into the funnel ( add few extra ml of oil). It takes 50 minutes for 650 ml of gear oil.
6- When oil is cleared the funnel, use bicycle pump to push the oil further.
7- As soon as the oil cleared the hose, bend and kink the hose quickly to prevent oil from flowing back to the hose. Use tie-wrap to keep the hose kinked.
8- Get under the car, have the drain plug within reach, remove the fitting and plug the hole with finger. Grab the drain plug, remove the finger and screw in the plug.
9- Tight up the plug and you are done.
You will loose some oil so you added few extra ml. Make sure to go from fitting to finger then finger to plug or if you not fast enough you will loose a lot of oil and bigger mess.
If you have a pump then pump it instead of gravity feed then it will be faster. Hope this will help some one.

There is no requirement to change diff or transfer case oil. They are filled for life. Why did you do it?

The weak link is the transfer case, but failures are traced to bad assemblies vs old oil.

In my understanding of the W221 7G 4matic transmission, the transfer case is lubricated from the main gear box - It's integrated. The high failure rate as seen on 7G integrated 4matic transmissions (Check the GLK forums) is due to oil starvation to the integrated transfer case.

I'm not sure what you have done? It may have a drain plug - But it's not meant to be used in the way you have.

- I speak from experience having serviced my old w211 4matic, And having had the entire transmission replaced in my 2010 s500 4matic due to a worn bairing.

Thanks very much for DIY that is what I am planning to do to my 08 S550 4Matic.

I have two questions before acting to my car.

1) What kind gear liquid you were using to your S550. I am planning to use Lucas 75W-90, but MB recommand 85w-90.
2) Where is the front differential location ? Should I remove the front bottom rubber panel or the rear one only ?

Thanks.

Isn't the transmission oil also filled for life?

No, blue fluid gets changed/flushed at 80K and red at 40K. Depends on the vintage if transmission.

I used what MB recommend.
It is located after the steering rack-n-pinion and I can not remember what panel to remove.

Bringing this back! Thank You to the OP for posting this. I searched all over looking for a DIY on this. Everywhere I looked it said "remove the axles"to fill the fluid. I threaded the fitting as described. Worked great! My car needed this as the fluid came out black at 100k miles. Mercedes what are you thinking by not having a fill plug?

It appears that Mercedes ATF filler adapter is M12x1.5mm, so it can fit the front differential drain hole. You can use any hand pump based fluid dispenser to dispense gear oil into the front differential through the ATF filler adapter.

I found a video for quickly removing and replacing an oil pan plug - . This same procedure can be used for removing the ATF filler adapter and quickly installing the drain plug without losing much fluid.

I have a w212 4matic which has the same issue with front differential - no fill plug, only a drain plug. I plan to try the ATF fill adapter.

Thanks for the post, I changed my front and rear differential fluid today.
I used the Transmission Fluid ATF Fill Adapter to fill the diff with a standard hand pump.

Thanks for the post

Found this, will this fit?

I only did it this week and used an adapter at the front with which I can now change the oil without any problems. Now use the rubber tube, injektion and Stahlbus® oil drain valve
Translated with googletranslate
Greats from Germany