by Chris Warren, AK, Mo, Mug & Tyrone
Tools & materials
1. 14mm hex socket wrench (allen wrench)
2. Differential oil (ETK says 1.2 Liters), we used 2 bottles of Mobil1
3. Suction Gun to fill with new fluid. (Purchased at AutoZone for $15)
4. BMW recommends replacing the drain/filler plug sealing rings.
1. Drive car around long enough to get the differential up to operating temperature.
2. Jack up rear end to get access to drain and filler plugs. If you use the differential as the jack point it's probably a good idea to avoid putting the jack on the rear cover and use a pad like a wood block to ensure the corner of your floor jack doesn't stress the differential housing. Use jack stands under both rear jack points which are in front of the rear wheels on the frame.
3. Loosen filler plug using 14mm hex wrench to allow minimal splash during drain. Located at the upper rear of the differential.
4. Remove drain plug using 14mm hex wrench. Located at the lower passenger side.
5. Allow fluid to drain completely (We pumped few ounces of new fliud into the fillter hole to help flush out all the old fluid).
6. Replace drain plug. Tighten drain plug to 70Nm. (50 ft lbs)
7. Add differential oil until overflowing
8. When overflow from filler hole has stopped flowing, replace filler plug and tighten to 70Nm. (50 ft lbs)