Try having someone else shift while you listen under the car to see how far back the noise is coming from. There is a crossmember underneath that you can use as a point of reference. As you can see here and below, the crossmember is roughly where the middle universal joint is (the bolts coming down from the body on the left and right are where the crossmember bolts on). There is also a similar joint at the very rear of the driveshaft.
Black 2007 Alpina B7
Tension strut bushings
White 2007 Alpina B7
Supercharger clutch/bearings, replaced exhaust valve/pulled head, sunroof seal, 6000K angel eyes
Black 2002 BMW 745Li (sold)
KW v3's, blue angel eyes, 8000K headlights & HID fogs, rebuilt alternator & mounting bracket gasket, sunroof seal, CCVs, plugs, sway bar bushings, timing & valve cover gaskets, valve stem seals, guibo joint, mechatronic sealing sleeve, trans fluid, sanded headlights...