Hello,

I drive a 2010 GLK 350. I leave the trans in "C" shifting mode all of the time. Whenever I'm out driving, the car will switch gears on me, dropping into D2 or D3. Sometimes even to D1, which scares the hell out of me on the highway has got to be hard on the transmission. This doesn't happen repeatedly, but it is inevitable that it will happen at least once if I'm driving for more than a half hour.

Nothing is getting nudged or bumped. Both hands on the steering wheel. And it happens to both my wife and I equally, so I don't think it is the result of any peculiar driving behavior. For the past 5 years I have mentioned this problem to the service station every time a service is due. They haven't been able to reproduce it, though they tell me they don't have time to do much more than drive it a mile or two down the road and back.

I've Googled and poked around this forum as well, and I haven't turned up any answers yet.

Any idea what could be causing this? I am worried that it's going to eventually lead to some serious transmission damage.

Thanks in advance for any insight.