Hey darks,
Just a guess, but, I think the drive shafts are "balanced" from factory. This applies to re-installation of the the old shafts (mainly the two rear drive shafts).I always make an alignment mark on mine if I have to remove them. Unless the splines are keyed, you may want to take the new ones to a shop to get them balanced if it hasn't already been done by your parts/rebuild source. I say do it right since your putting the effort forward. It might be overkill, and others can comment. Its a small radius, rotating mass, but if its off by alot, could drive ya nuts with vibration and all and work against all the fine work your doing.

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2005 X5 3.0, 6MT, Alpine White on Truffle Brown, Sport, Preim, and Cold Weather, Alpina Stainless Headers, AFe Intake, UUC SSK, OEM 87's, 3.64 Differential Swap,Performance Modified Euro 2 Tune, UUC LTW Flywheel and HD clutch, Bilstein B12 Suspension kit
Future mods ZHP/Schrick Cam Shaft upgrade, Operation code name:Doppelschrauben-Kompressor

Wife's Ride: 2011 e70 X5 351 M///Sport.

Also in the fold: 2004 X3 3.0, 6MT, Black Sapphire on Terracotta, port, Premium, Cold Weather.