I have a 1997 528i and the trany randomly shift down and stays there, we can move the shifter around from drive to s3and so on but it seems to have a mind of its own. It seems to happen when its rainy out. I have changed the trany filter and fluid but it still does this on random occasions. I am thinking it could be the position switch on the side of the trany, does this sound like a good place to start?

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: BMW Automatic Transmission Fluid Change

It could be the shifter mechanism, but it also could be related to the traction control system on your car. I have a 1998 E39, and it has built-in traction control when the wheels spin on wet surfaces. This doesn't happen a lot, so I don't really have very much experience with it, but one or more of your wheel sensors may be faulty, resulting in problems with the car deciphering the road conditions. This is just a best guess...

- Wayne