Having just bought this car and not having very much info on past service I am looking to get a few things done. The car has 38k miles on it and it should have had the differentials serviced at 30k miles. I was just curious if it is routine to have both front and rear diffs done at the same time? The dealership quoted me $310 for the rear diff and $1108 for the front diff. They said if the front diff has any leaks it would be another $3685 to reseal it but the car was just inspected by the pervious dealership and has no leaks that I am aware of so I am not too worried about that. They also quoted me $1152 for a transmission fluid and filter change. I don't mind paying for the work but I was just looking to get an idea if this sounds about right.

My own experience 21 E63 though I avoid dealers as much as I can:

Rear diff - did the work on my own at about 25 k miles - three or so bottles of Castrol Transmax 75w 140 ran me about $50 to $60 all in. Took me about an hour but I was going real slow cos it was the first E63 rear diff I was doing. Guess if dealer rate is 275 to 300 per hour then your quote is in the ball park.

Front diff - That's supposed to be sealed and you can only get to it supposedly by removing the right side front axle - happy to be corrected if not so. I had mine done under extended warranty at the dealer because it started to leak - that worked out real good for me - zero cost with a full front diff service. Was told that fixing that leak would have been in the high 5k area without my extended warranty.

Tranny fluid change: done at an independent and I supplied parts/fluids Tranny pan, filter, 10 liters Liqui Moly Toptec 1950 tranny fluid, some tools and adapters for the job - roughly $300 for parts. Labor at my indy guy was about $350 but that included a transfer case fluid change too ( note the transfer case fluid is a different fluid than the tranny - think back to the older 7 speed MB trannies from the mid 20-teens - it is that fluid - Fuchs Titan 7134 FE was what I used ). So I got away with a roughly $700 or so parts and labor cost for my tranny service and the transfer case.

Just as a reference point - had my rear diff and transfer done at 60k by an independent in NJ for under $700 last year. Transmission was done at 55k by prior owner, so that'll be good until 90k interval.

Front diff isn't on any service interval I can find, so as OBP mentioned, would only tackle that if there was a problem.

Your front and rear diff service costs are comparable to what I paid here on the San Francisco peninsula. As noted above, the front diff is more expensive because the work is done through the axle shaft. Mercedes has no service interval on the front diff--which is probably why the engineers made service so stupid... although maybe there's some design reason drain and fill holes were a no-go--but my dealer tech said it should be done with the rear diff. That's likely conservative since the front diff sees less rigorous service than the rear diff.

The service schedule for the S213 is pinned somewhere. I posted it a year ago and the admin pinned it. A discussion of the front diff is also in that thread.

Some just use drain hole with the same amount of fluid. redline 75w140 LS. ( this is what I was told ) I’ll try this shortly need to do front diff and transfer case I’m at 93 K miles

I am happy to report back that I was able to get the front and rear diff service done for $443 at a Mercedes dealership. However this is not a typical price for this work to be done. After receiving the first quote I called another dealership who quoted me $443 for front and rear and I booked an appointment. This price seemed very low to me since the first dealer quoted so much higher so I called the the second dealer back to verify before taking it in and they confirmed the quote was accurate. So I take it in and after waiting for about 2 hours the service writer comes and and tells me it will be an additional 2 hrs labor because they didn't factor in having to remove the two front CV axles to get access to the front differential. I told them that I called and verified the price before coming in. The service writer spoke with his manager and they honored the quote. So I got a deal but for anyone else I would expect to pay around $1000- $1200 for this service to be done.

That's an excellent price. You did well.