I trust you generously greased the splines on your front driveshaft before reassembly. One of your first photos seemed to show a fair amount of rust there that could indicate advanced internal wear of the splines. Great job with the thread though.

2002 X5 3.0 307,700 miles
2014 428i 21,200 miles

2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles

1970 Firebird - Under restoration