BMW lifetime cycle for these gearboxes is wowfully IMO wide if the mark, we do shed loads of sump/fluid changes on E90's E60's incluiding Seb(ESS's) and other when inspceted the sumps are leaking as are the mechatronic sleeves.
Its not unusal to lose a good litre plus of fluid say over 5-6 years 80k(ZF recommend every 50k that the fluids changed and also with these cars ideally due to the way they leak the sump/filter combo) Mercedes and VW/Audi as manufacturers do a better job re ensuring their transmissions stay together by recommending fluid changes every 40k or so, which a lot of their customers actually do understand.
Quite why BMW went the sealed for life route remains a mystery, but put it this way if it was sealed for life then you'd expect difficulties in getting fluid/sump filter units yet call BMW for say a sump in the morning you'll have it in the afternoon and most dealers have fluid on tap or again can get it same day, so if its sealed for life why the hell would this stuff dealer wise be so accessable!
Stange. But moving on as an indy dealer we recommend every 50k or so miles the units changed, which is in line with ZF, when we service cars we always inspect and usually we find & report any leakage. Customers for instance sometimes report coming to a halt and expieriencing a thump from the transmission or delay's or abruptness re gear changes, usually this is all we need to look and usually we discover leakage.
When drained the fluid looks like this
dark, smelly and corupted by heat and other matters which means clearly the fluids not working as efficiently as it should hence the issues customers face. If you look at how shiny the sump is below
this is sweeting fluid that coated the underside of this particular sump(the sleeve was also coated in leaking oil-which is very common) So how can this last a life time
This is how the sump should look in place
Clean withno oil trace whatsoever.
Once the fluids changed
its recommended that the cars adaptations are re set for gearbox(via diagnostic)but as I've also discovered the other day re set the engine adaptations as well as this makes when combined a hige diffference as trhe engine ECU's taking to the gearbox ECU, both of which have become acustomed to the car driving with dirty leaking fluid over time. Re set these and the car with new fluid will adjust to its new fluid and trust me it really works.