Replenishing rear differential oil:

WARNING: This page is about a different car, the 2005 BMW 745i, 2004 BMW 745i, 2003 BMW 745i, and 2002 BMW 745i. However, it is still accessible from the selected car via links, so may be relevant.

Undo oil filler plug (1).

Fig 1: Locating Oil Filler Plug

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Check rear differential oil level.

If necessary, pour in rear differential oil up to lower edge of opening for oil filler plug (1).

Installation:

Fig 2: Identifying Oil Filler Plugs

Courtesy of BMW OF NORTH AMERICA, INC.

Oil filler plug with sealing ring:
Replace sealing ring (1).

Tightening torque, 65 Nm.
Oil filler plug with O-ring:
Replace oil filler plug (2).

Tightening torque, 60 Nm.