Alright, this may or may not already be on this forum, but I have not found it here.

To change your rear diff fluid on a 2014 E350 4Matic sedan you will need these:

- H14 Hex socket or wrench
- Swivel adapter for whatever size socket you use
- 3" socket extension
- If you are doing this on jack stands, or ramps, you will need a rubber mallet or impact of some kind.
- 75w90 2L gear oil, I used Lucas brand. You will hear arguments for 75w85, it makes little difference, get the OEM if you want to spend double.
- Fluid transfer pump ($7 at Harbor Freight). https://www.harborfreight.com/multi-...ump-63144.html

Steps:
- Get the car in the air using whatever method you have.
- Locate the drain plug, attach the swivel adapter to the H14 socket after cleaning the drain plug socket hole out thoroughly (or the socket may not fit).
- Jam the H14 and the swivel in the hole on the drain plug on the passenger side (US) ABOVE the passenger exhaust, wriggle it around a bit, I suggest using PB blaster to make sure it's fully seated.
- Connect your extension as you'll find the ratchet won't seat above the exhaust even with the swivel.
- If this is your first time changing this in 5-7 years you'll need a rubber mallet to whack the ratchet counter-clockwise (some will balk at this, relax, use a solid if you want but I've been abusing my harbor freight grade ratchet for years like this and haven't broken it).
- Break the plug loose, but DO NOT fully undo it.
- Alright, now for the fill plug, you'll find it on the drivers side (US) of the differential, slightly forward and above where the drain plug is on the opposite side. You can use a standard H14 socket and ratchet for this, no need for extensions or adapters.
- Use similar methods mentioned above to break that loose.
- Now, remove the fill plug completely first, all the way out.
- Then remove the drain plug (not a large amount of threads, have the catch pan ready).
- Clean both sides of both the drain and fill plug with some paper towel, then some brake clean.
- When the fluid is completely drained pop that drain plug back in using the same method mentioned above to remove it, torque it down quite a bit using the same hand tools (yes, you can reuse it, I've done so twice with zero issues). Find the torque specs somewhere if you want, I haven't cared to find them, "good-n-tight" works for a differential plug.
- Now put the fill line on your transfer pump into the diff fill port and the draw line into whatever bottle of fluid you're using, and pump away, you cannot overfill this differential.
- Keep filling (takes roughly 1.1L) until it starts spilling out of the fill hole.
- Once it slows to a slow dribble pop the fill plug back in there and torque it down in a similar fashion to how it was removed.
- Clean up the huge mess you made somehow.

Done.

Hopefully this helps somebody somewhere who cares about their Mercedes.

 

Good info. Just want to make sure the diff is level. In other words, use a lift, or get the car up on 4 jack stands. No jacking up just the rear for access. I use my Mighty Vac to push the new fluid in, but those hand pumps are also effective.

 

Great write-up, thanks for that! Good move making sure the fill plug can be removed before doing the drain plug. The last thing you want is an empty diff and no way to put new fluid in!

I use this style pump for this sort of thing and it's worked great for me. Cleanup is always really quick and easy. You can get them at most auto parts stores. It even screws onto some diff fluid bottles.