In the case somebody else finds this thread on a search, I just did this repair today and it is not difficult to get the spline back through the hub:

1. clean both sides of the spline
2. Oil both sides of the spline
3. start the bolts into the flange while starting the spline mesh
4. with the flange bolts loose, reach in to the drive shaft and pull outward
5. while the flange is outward, knock on the hub with preferably a dead-blow hammer
6. each tap should move the spline about 1-2 mm through the hub
7. when far enough in, use impace wrench to tighten the 36mm axle nut.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)