In a previous posts I described the "Park Module" going bad on my i3, and I'm gaining a little more understanding of what it is / what it does.
So in reality this is part # 27217645837, and is referred to as the "transmission motor actuator" or "transfer case motor," among other things. There are a lot of actuators on the i3 so the part number is the most reliable reference.
Here's a video of it in assembly, and it offers a peek inside the case before it's sealed up. The the big black plastic thing nearest the camera, bolted to the side of the transmission case.
Whereas up to now I was thinking it was a pawl of some sort that jammed into the transmission to prevent the car from rolling, I see now it's a servo of sorts that rotates a shaft that most likely selects D / N / P -- I'm guessing. Perhaps the better name is "drive selector." The label reads "PS Aktuator"
So here's my question: What if any damage is being done when I park the car, engage Park, but neglect to set the parking brake, thus allowing the car to roll slightly forward or backward? To me it feels like I'm binding up the Park mechanism, in a bad (i.e. potentially damaging) way. Up to now I was considering this may have led to my actuator going bad, but with a better understanding of how this works, I no longer think that's the case.
But now I'm wondering if something inside the gearbox is picking up that load, potentially causing damage.
Obviously the solution is to set the parking brake consistently. I try, but every now and then I miss.