Where is the transmission fill plug?
 

Have you wondered? Done a search on the direct terms and found nothing? Well, here is to help you out.

The wagon version, 530xi touring, four wheel drive with an automatic transmission has its fill plug at the left rear corner of the transmission. On US version that is the driver side. The plug is 1 inch above the oil pan gasket surface and requires a 8mm allen socket. It is totally obscured by the coupling drive from the gear box to the front 2 wheels. In order to get access to this plug, you need to remove 4 torx bolts from the coupling drive and the shaft will hang down. Be sure to put it back in the exact location.

One picture says a thousand words, and could have saved me two freaking hours.

Did you reuse the old torx screws when you reattached the drive shaft? what is the correct torque for the screws?