WARNING: This page is about a different car, the 2010 BMW 135i, 2009 BMW 135i, and 2008 BMW 135i. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Drift (23 2 220)
Courtesy of BMW OF NORTH AMERICA, INC.
NOTE:
For bearing of countershaft shaft in front and rear section of transmission casing