I didn't see a DIY, so I figured I would make one. Here's what you are going to need for the diff fluid swap:

Difficulty 3-4/10



14mm Hex Head Socket
Ratchet
Torque Wrench
Recovery Container
2 Quarts of your favortie 75W-90 Diff Fluid (I used Mobil 1)
Fluid pump. (I have a mityvac, and highly reccomend them to anyone with anything german)
About an hour of your time

Take your time, and make sure that you do things correctly. I am not responsible if you break your car following my guide blah blah blah.

Step 0: Take your car for a drive to warm everything up.

Step 1:
Jack up your car



Step 2: Locate your Diff. It's the thing inbetween the axles, about the size of a watermelon with a big ///AMG heatsink attached to it.



Step 3: Locate the fill plug, and pop it open. It's the weird looking plug with a 14mm hex socket on it. THIS IS IMPORTANT. IF YOU CAN'T OPEN THIS, YOU CAN'T REFILL IT, SO DO IT FIRST.



Step 4: Place recovery container under your diff's drain plug, and pop it open. Word of warning, diff fluid is possibly the worst smelling fluid in your car. As you can see, my fluid was black, and probably the original fluid. The fluid should be a light amber, almost the color of brake fluid.



Step 5: Lower car, and let it completely drain into your recovery container. Just let it drip for like 10 minutes or so. This would be an excellent time to enjoy a beverage, like something in a pineapple with a tiny umbrella in it. I took the time to suck out the drain container with my mightyvac and put it into an old oil contianer for later disposal.



Step 6: Jack up car again, and replace drain plug, Torque to 40lb/ft.

Step 7: Insert pump hose into fill hole, place recovery container under diff again. Now is a good time to clean off the face of the fill plug, mine had black gunk all over it.



Step 8: Lower car, and begin pumping in fluid. It should take a little over a Quart. Stop pumping when fluid starts to drip out of the fill hole.



Step 9: Jack up car, and remove hose. Reinsert fill plug, and torque to 40lb/ft. Lower car and test drive. Enjoy your new diff fluid!

 

Great! Will be doing this to my newly acquired E55. Thanks!

 

Great write up! I'm assuming this is for the stock diff. Would the process be similar with something like a Quaife LSD?

 

I'm not familiar with that diff, but most are pretty much the same process. The diff is almost identical to the one on my mom's E350 though.

 

great writeup! - this 'could' potentially give you some MPG improvement and reduced track times because of less 'friction' with newer fluids