Got grease all over your under carriage near the rear differential?
It's the driveshaft! BMW decided to use a non-servicable driveshaft and a CV joint grease fitting ... two things that don't go well together. Like clockwork, around 100K miles, the seal between the rear differential flange and the driveshaft CV joint can fail sending now liquified grease flying everywhere. It can create quite a mess and puts your whole drivetrain at risk of failing.
If you take this problem to a BMW dealer they are going to recommend that the whole driveshaft be replaced at a cost of over $1500 (at least they did when I brought it to them)!
In all cases I've seen, the driveshaft is fine and it's simply a combination of a $10 seal and repacking the old CV joint with grease to correct. The only problem is to get to the CV joint you need to drop the entire exhaust system. If you are gonna tackle this as a DYI be sure to set aside the whole day.
I recommend Redline CV-2 grease packed into both the driveshaft CV joint and differential flange. You can apply it on a small piece of cardboard to really work it in there. i was able to get about 3/4 of a tube in before sealing everything up. You can get the part number for the seale from www.realoem.com and order it at any BMW parts counter.
2013 Ford Edge SEL AWD
2012 Jeep Grand Cherokee Laredo 4x4
95 e36 M3/5spd, 96 328is/5spd, 97 540iA, 98 528iA, 01 X5 4.4iA, 03 325xiA, 04 530iA, 02 330Cic/5spd, 08 535xit