HP Autowerks supplied the Output shaft seal with my Wavetrac diff. That's a good thing because it was pretty tough to get them out
I saw no need to replace anything else.
'08 E90 335i 6MT. VM 6466g2 kit. Stage3+ Fuel-It with FPR return, BMS PI injection, widebody
'09 Z4 sDrive35i DCT, MHD Backend flash, JB4, DCI