Well, I'm about a year too late, but I finally got around to changing the gear oil in my 535xi's front and rear differentials. If you want to do the same, here's what you'll need:

14mm Allen Socket
14mm Wrench
8mm Socket
10mm Socket
16mm Socket
Phillips screwdriver
Plastic Tubing or Racking Cane
Fluid pump
2 quarts Red Line 75W90 Gear Oil

Please use these notes at your own risk. This is not an idiot-proof procedure; I've left off steps if I consider them to be obvious- my standards may be different than yours. Remember, I'm not a BMW technician, just a dude with some hand tools and a strong desire to save money and make my car last a long time.

Rear Differential:

Unlike previous generation BMWs, the E60/61 cars don't have a separate drain plug. There's just a fill plug. Here's what it looks like:



The plug is on the rear of the differential. It's a 14mm allen bolt. I used the allen socket to get it off. Sticking my finger in the fill hole, I could feel the oil level just below it's bottom. To get the oil out, I stuck in a plastic racking cane pilferred from my other hobby, homebrewing. You can use plastic surgical tubing, but the angle on the cane was perfect for hitting the bottom of the sump. Start to siphon the oil out, using whatever suction means you consider appropriate to start the flow. Here's what the old oil looked like coming out:



Yuck. It takes a little while for it to come out. If you have access to a suction pump, it will go faster. I didn't. Once drained, I took my cheap FNAPS suction pump and promptly discovered that the neck on a Red Line oil bottle is not "standard size". So, I scavanged an empty oil bottle off the drain rack and poured the gear oil into the empty bottle. Here's my set-up:



The differential took almost exactly one liter before oil started dribbling out the hole. I let it weep out, then reinsterted the plug and tightened until snug. All done!

Front Differential:

The first step is removing the aerodynamic cladding that covers the front differential. The only panel you have to remove is the one that's attached to the front plastic fairing. It's fastened by a variety of screws- 8mm, 10mm, and phillips screws. Once you get that off, you'll see a bright metal skid plate held in place by six 16mm bolts and one 8mm screw. It looks like this:



Now you're face to face with the front differential. Surprise, surprise! It has both a drain and fill hole! Apparently the engineers figure that if you go through all the effort of removing the cladding, you deserve a break. Warning- be careful not to confuse the oil sump drain and the differential drain! The oil drain is a hex bolt; the differential drain uses the same allen key you used in the rear. Remember, always loosen the fill plug before the drain plug! The drain plug is on the drivers side of the diff.



Once the drain plug was out, I removed the drain plug on the bottom of the diff:



After letting it drain, I re-insterted the plug and filled using the same pump as in the rear. The front took about 800ml of oil before overflowing.

I'd intended to change the transfer case oil, too, but was scared off by the amount of interference blocking the fill hole:



Think I'll leave this one to the pros. The drain plug is easy, though:



I also took a picture of the transmission fiilter housing- I haven't quite worked up the courage to do an ATF service on my own.



Once everything is back together, relax with a frosty beverage of your choosing!



SportUniversaal