Thanks chaps its all great information. I really like the Giken diagram.
I am still stuck though as to the differences between the e46 m3 and z4m diff...
I did find this which is from the manufactur that built the diff for the m3 not sure if they manufactured the one in the Z?
http://www.gkn.com/driveline/about-u...coLok-engl.pdf