This is a well-known problem on both BMW and Mercedes cars. Mechatronics or ConductorPlate+ValveBody houses the valves that control the transmission. There is an electrical connection on the side of mechatronics (or conductor plate and Valvebody) and connects to transmission controller/TCU. The bushing/sleeve/gasket is supposed to prevent trans fluid leak out from that electrical connection. Due to age/temp/manufacturing defect, that bushing/sleeve starts to leak trans fluid. On BMW, that connector is not so easy to reach with the trans pan in place. So, they drop the pan, reach in to the connector, replace that bushing and put back the trans pan.
I have replaced that bushing on all Mercedes cars/trucks I owned at least once on each vehicle. On BMW, it hasn't started leaking yet. Every time my car is on the hoist, I look for leaks around that electrical connector on the side of trans pan.
BMW/Mercedes dealer will charge around $700 for replacing that bushing/sleeve. Part is less than $20. Once you understand how that sleeve/connector works (twist on the tab, pull-out), it's an easy DIY job.
Last edited by pcy; 11-30-2011 at 11:40 AM.