My local Mercedes Benz dealership states that the transmission on my car needs to be serviced every 39k miles. The service manual states the same thing (Automatic transmission - oil and filter change). Another local service center (not Mercedes authorized) stated that although the book says to service the transmission, the fluid type states lifetime service and they do not want to replace the fluid stating that it is meant to be lifetime (left alone). Can you please shed some light on this?
I would lean towards the manufacturers reccomendations. As far as lifetime transmission fluid, I am not a bleiever in lifetime products. With lubricating oil their is always contamination and viscosity breadown over time.
I Mercedes reccomends changing it, what fluid are they looking at that is lifetime fluid? Why is it even available? Is it only for when you rebuild a transmission?
There are clutches in your transmission which eventually where out just like a manual transmission clutch. The material from this ends up in the fluid and affects the lubrication protection. Also, during break-in, some metal gets shed off into the oil. Not as much as in an engine, but it happens. There is no such thing as a perfect seal either. If it can leak, contaminants from the environment can get in too.
Some synthietics claim over 100,000 miles of service when a special oil filter is used. And the filter is the size of a propane tank.
So, this shop is basically saying they cannot service your transmission in any way. I think you might want to take it somewhere else.
You can find transmission shops near you using this site. When you search the site, links come up that relate to the search and if it inolves a repair facility, it is actually ones in your area.
So, get your oil and filter changed by someone who is confident in doing so.