Drive shaft replacement

[skiwi]

2001 325 277,000 miles auto

So it's time to replace my drive shaft after having replaced donut, center bearing, trans mounts to eliminate the irritating vibration. My mechanic confirmed it's worn universals.

I'm going to buy a reconditioned DS (new UJs/center bearing). The next to useless Chilton manual I have says that you should mark the differential flange to drive shaft flange before dismantling. Í know the DS is a 2 piece, balanced affair, which needs to be put back together exactly as it is taken apart for reasons of balance, but wouldn't have thought it needed to be mated to the diff in any specific orientation. Anyone have any input on this?

Also, Realoem doesn't show the nuts that screw on to the back of the torx head bolts that join the DS to the Diff. Does anyone know the part number for these?

Thanks for your assistance.

[Stinger9]

few mechanics really could explain all scientifically. But I have heard that what you say is so. Can't imagine why this makes a difference, but it's free to mark things to replace them in the same orientation, so why not?

Balance is critical here with something potentially spinning at 6000 rpm, so I'd make sure the rebuild shop had good credentials with regard to balancing.

Are you sure there is a nut on the other side of the diff flange? Seems I recall seeing diff flanges that were tapped with threads.
Maybe spot an undercarriage shot in some DIY to confirm. Or look under your car.