Car in Park: Rollback Damage?

[eNate]

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.

http://www.****oodog.net/images/i3/drive-actuator.jpg

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.

https://youtu.be/PUr2DL0ny5o?t=236

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.

 

[electronchaser]

you basically wrote what was in my head. lol.

I've got the same concern as I'm getting used to an e brake without the auto H functon.

At times I've missed hitting it, I've felt a harsh thud into park. made me cringe that I damaged something.

Other times, I'm faster than the gear selector and I think I've put it in drive, I release the brake only to feel it roll back and give a weird mechanical groan as it was still in P and it rolled about an inch back.

I'd love to know as well.

 

[eNate]

I haven't found the answer to my question yet, but I'm figuring out how the Park function works on the i3 gearbox and posted what I found on another forum that helped me get the car into Park to begin with, when the system began acting up.

In case anybody is curious...

https://www.speakev.com/threads/bmw-i3-drivetrain-error-wont-go-into-park-fix-for-free.143865/#post-2781545

 

[electronchaser]

did it again last night by accident on a relatively angled spot, where I rolled back a good 2 inches before lock engaged. But when I came to drive off later, shifting it into drive, I didn't get that classic harsh jolt that you do in automatic cars if you let the car rest on P on a slope. So I'd still Like to know if i'm messing anything up. I wish the brake button was positioned a little more practical.

 

[robthebold]

Even in a traditional ICE powered car, I'd be a little worried about just rolling back against the parking pawl. Welded to the bell housing or not, I'd think you could break it off in the worst possible circumstance if you don't engage the parking brake. And why find that out in the harshest possible way?

But re: the i3. My parking procedure is to engage the parking brake and then shut off the car. Turning off the "ignition" automatically sets the gear selector to "P". Now that I'm used to that, the three step process of "select Park, engage brake, ignition off"
in my wife's car seems needlessly labor intensive.

When pulling away, switching to Drive with the seat belt buckled automatically releases the parking brake. I'd been needlessly making my life more difficult before I figured this out.

 

[eNate]

There's just something particularly "bad feeling" about loading up on Park in the i3 versus any other car I've driven.

And then to have my Park Actuator go bad...

But the Park detent is connected to the input shaft, so the rolling car should have very little leverage to abuse it. Plus the Park detent ring and tab lack hard corners -- everything is nicely rounded -- so there ought not be any pieces to catch and wear.

And it never seems to struggle, catch, or blind when shifting out of a loaded Park engagement -- I **have** felt that in other cars. So I guess it's designed well?

I'm 100% down with your policy of setting the parking brake first, but sometimes my cadence is off a tick.

 

[alohart]

But re: the i3. My parking procedure is to engage the parking brake and then shut off the car. Turning off the "ignition" automatically sets the gear selector to "P". Now that I'm used to that, the three step process of "select Park, engage brake, ignition off"
in my wife's car seems needlessly labor intensive.

Why not simplify your life by merely pulling up on the parking brake? Opening the driver's door causes an exit from drive readiness state which sets 'P'. Locking the doors shuts off the car. The high-voltage system shuts off after several minutes.

 

[electronchaser]

But re: the i3. My parking procedure is to engage the parking brake and then shut off the car. Turning off the "ignition" automatically sets the gear selector to "P". Now that I'm used to that, the three step process of "select Park, engage brake, ignition off"
in my wife's car seems needlessly labor intensive.

Why not simplify your life by merely pulling up on the parking brake? Opening the driver's door causes an exit from drive readiness state which sets 'P'. Locking the doors shuts off the car. The high-voltage system shuts off after several minutes.

I've tried to memorize this exact sequence, but its hard when switching between diff cars. Plus there's those times when you want to set the climate and if you open the door the prompt goes away (even though I have it programmed as a shortcut).

When i do remember, I pull the parking brake and hit the start stop button which also puts the tranny in P. Still preserving the climate thingy, and doesnt cut stereo allowing to finishing up a track if its a good song !

I just really wanna know how the mechanism works, because there's a disturbing rollback when forgetting to engage P brake. But at the same time, there's no jolt, or any other mechanical/physical sensation when shifting back out of park after forgetting the P brake.

 

[MagicCarpet]

If you can search for "BMW Group University technical training ST1403a" then download "I01 High-Voltage Components"
see page 38 for picture of parking lock pawl and gear

As you suspect, it is not a good idea to wind up this system if that can be avoided by pressing P when the vehicle is at a stop and also pulling the parking brake if on any slope.

 

[eNate]

If you can search for "BMW Group University technical training ST1403a" then download "I01 High-Voltage Components"
see page 38 for picture of parking lock pawl and gear

Hey, Magic, thanks for that link! Very detailed goings-on in there.

Below is an diagram of the transmission I took from the manual, and I'm also a few screenshots I captured of the actual parts from the BMW video showing the assembly of the i3.

On page 36 the maunal states, "...on steep inclines / downhill gradients up to 32% the parking lock is able to safely hold the (i3) at a standstill. " Looking at the very slight bevel cut of the lock mechanism, this makes me believe the "rollback" of the car will never bind it up so much that it can't release, and that with enough force (parked on a slope in excess of 32%?) the force exerted on this lock may force it to pop out of place.

Secondarily, any abuse will never directly impact the Park Actuator, though I still wonder if I bind it up, will that increase the actuator's torque requirement to the point that it taxes it? No matter, I just need to work on being consistent applying the parking brake.

https://www.leschroniquesdegoliath.com/wp-content/uploads/2018/01/Mercedes-06_I01-High-voltage-ComponentsGB.pdf

http://www.****oodog.net/images/i3/transmission.jpg
http://www.****oodog.net/images/i3/transmission-list.jpg

http://www.****oodog.net/images/i3/i3-park-lock1.jpg

http://www.****oodog.net/images/i3/i3-park-lock2.jpg

http://www.****oodog.net/images/i3/i3-park-lock3.jpg