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Discussion Starter · #1 ·
Today I parked my ascent in front of my house pointed hood first down my driveway. Normally I park hood up the incline but was unloading groceries and firewood. Definitely put the car in park, made multiple trips inside and unloaded everything. Later in the afternoon looked out the window and car was gone.
found it at the bottom of the hill caught on a tree. One foot to the right and it would have gone over a tall bank into a stream.
Car was still firmly in park.
obviously we can fix the damage but WHY did it just roll away about 150 feet at least. Is there a black box thingy that can be analyzed? I am really hesitant to drive it again after this.
currently I have large boulders stuffed under the tires.
 

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How steep is your driveway? Do you have any neighbors with a doorbell camera if for nothing else but to rule out foul play?
 

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Discussion Starter · #3 ·
How steep is your driveway? Do you have any neighbors with a doorbell camera if for nothing else but to rule out foul play?
About average slope not extreme but not flat. Definitely no foul play as I live in a private location with no real neighbors.
I used the x mode for first time today, as it was snowing. I thought it felt funny as I was backingup in front of my garage. I was back and forth several times unloading so it didn’t roll away then .
is there an onboard computer that might have recorded the event?
 

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is there an onboard computer that might have recorded the event?
Some info is stored but I don’t know the depth of it. It’s not as detailed as an airliner black box of course. Was the engine on or ignition in the on/ACC position?
 

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About average slope not extreme but not flat. Definitely no foul play as I live in a private location with no real neighbors.
I used the x mode for first time today, as it was snowing. I thought it felt funny as I was backingup in front of my garage. I was back and forth several times unloading so it didn’t roll away then .
is there an onboard computer that might have recorded the event?
If your car was actually on (and it detected the impact), yes. If it was actually off, no. Most common cause I've seen is the car being turned "off" while in drive or reverse and then being left. It's not off, and it's not in park. Once, it's a snapped parking pawl, but, one can usually hear that - that's most commonly caused by people who don't know how to engage the electronic parking brake.

In any event, please remember next time to follow the instructions in the manual that indicate you should use the parking brake all of the time.

Please keep us posted about what you find out. I'd love to know what caused yours. Did you take pics of the area and aftermath of the event?
 

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If the car was in park the whole time, it might be good to have your dealer check out the transmission to ensure the parking pawl works as it should and did not break. Yes folks always say you should have the parking brake on but the transmission should have held fast unless your driveway is very steep.
 

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With regard to the parking brake be sure to put it on before you take your foot off the brake pedal. This way you are not putting undue pressure on the CVT. Also can you actually turn off the Ascent without it being in Park? With mine the engine turns off but the displays remain on with along with an alarm sounding.
 

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If the car was in park the whole time, it might be good to have your dealer check out the transmission to ensure the parking pawl works as it should and did not break. Yes folks always say you should have the parking brake on but the transmission should have held fast unless your driveway is very steep.
It would seem to me rolling in the snow like that would require applied force creating sufficient momentum, not just the lack of a parking brake. That photo doesn't depict steep terrain.
 

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Wow, that's very weird. No kids/neighbors/miscreants who may have been out for a joy ride? That's a very gentle stop into the tree, and the tire tracks everywhere make it look like people were having fun. Are there stores or neighbors with security cams who may have caught it on video?

Definitely have the parking pawl operation checked out. And let us know what you find out, please.
 

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Discussion Starter · #13 ·
Promise, no neighborhood kids, I live in the woods with no neighbors. The tire tracks were from me pulling in and then deciding to turn around and back in instead.
This is my second ascent, first one died 30 minutes after I drove it off the lot. They replaced it with this one. I am beginning to think that there is a serious problem with the Ascent.
 

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Promise, no neighborhood kids, I live in the woods with no neighbors. The tire tracks were from me pulling in and then deciding to turn around and back in instead.
This is my second ascent, first one died 30 minutes after I drove it off the lot. They replaced it with this one. I am beginning to think that there is a serious problem with the Ascent.

:( That sucks, sorry to hear that. But, no, it's not the Ascent line. I regularly park on steep to crazy and slippery/slidey inclines for photos. There's about two reports I've found anywhere of roll-aways, yours being the second.

7046
 

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Promise, no neighborhood kids, I live in the woods with no neighbors. The tire tracks were from me pulling in and then deciding to turn around and back in instead.
This is my second ascent, first one died 30 minutes after I drove it off the lot. They replaced it with this one. I am beginning to think that there is a serious problem with the Ascent.
Something is missing in this narrative. How far did the vehicle travel from where you parked it to the tree?

What explanation would you offer as to how the vehicle moved that distance with the snow friction on such level ground without the engine being on and no other active force placed upon the vehicle?

There does not appear to be lots of snow fall from the time of parking to the time of the photo, yet there is more than just a few inches on the ground. I know that any vehicle i had would have a difficult time moving at all on level ground in the snow without an initial force placed upon it. Even at that point it would need to be a somewhat sustained force for it to travel any significant distance.
 

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I think parking pawls are generally self-actuating. That is, once they're engaged even a little bit, they'll lock further in as pressure is added. Meaning, I don't think it's likely (or perhaps even possible) for the pawl to be "half engaged" and then fall out later. Though I couldn't say for sure, I think this probably rules out something like shift cable adjustment. If everything worked well enough to get the transmission into park and for the car to move forward and the parking pawl to "catch" that movement and stop it, and this had to have happened because you said your driveway is sloped and it didn't initially roll away, then I don't think a mis-adjusted cable or external part failure could cause this condition to "unset" itself.

If all of that above is correct, then there must have been quite the catastrophic failure inside the transmission when that pawl apparently gave way or failed (presumably accompanied by a loud and apparent bang). If the parking pawl failed, it should be immediately apparent to the dealer if they disassemble the transmission.

I don't know if you've backed it out from under the tree, but any apparent parking pawl failure as described above would almost certainly be accompanied by some pretty obvious symptoms now. I imagine there would be some pretty nasty noises as the car rolls or transmission rotates and/or "park" wouldn't hold the car today (if the parking pawl system broke).

If you have driven the car...does it appear to operate correctly now? Any noises? If you've tested it to see if "park" alone will hold the car (with supplementing it with the parking brake), does it hold?
 

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Discussion Starter · #18 ·
I backed it a few feet off the tree , but it didn’t want to go farther, wheels spinning on snow. There is a small ditch on the edge of the driveway that the front wheels were slipping on. I called some friends to come help and we managed to push the car over the ditch and back it up onto another part of the parking pad so that it would easier to tow. I wedged boulders under the wheels in case it want to go on walk about again. It is in park with the parking brake on. The driveway isn’t really icy as it is just snowing at this time. I will have it flat bedded to the dealership as I don’t really trust it.

I did notice that there is a blue liquid trail following the car, like coolant or windshield wiper fluid.
The damage is limited to the left front headlight area, not engine.
7047
 

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Discussion Starter · #19 ·
Something is missing in this narrative. How far did the vehicle travel from where you parked it to the tree?

What explanation would you offer as to how the vehicle moved that distance with the snow friction on such level ground without the engine being on and no other active force placed upon the vehicle?

There does not appear to be lots of snow fall from the time of parking to the time of the photo, yet there is more than just a few inches on the ground. I know that any vehicle i had would have a difficult time moving at all on level ground in the snow without an initial force placed upon it. Even at that point it would need to be a somewhat sustained force for it to travel any significant distance.
The driveway is definitely steep enough that if a car was left in neutral it would roll away downhill. I totally expected to open the car door and see the car in neutral and be the idiots who can’t park a car but it wasn’t and it was the very first thing I checked when I opened the car door.
7049
 

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I think parking pawls are generally self-actuating. That is, once they're engaged even a little bit, they'll lock further in as pressure is added. Meaning, I don't think it's likely (or perhaps even possible) for the pawl to be "half engaged" and then fall out later.
Back in the day, If the parking pawl is fully disengaged and sitting on the top of a geartooth, and the car was rapidly accelerated, it was possible to skip over the teeth. Earlier back, it was possible to snap the pawl on even slower roll-aways, or to bounce over the "gearteeth".

The continuous changes to the regulatory requirements and standards were supposed to address that, and, to my knowledge, have. It's also the reason why torque lock is much easier to accomplish (car stuck on parking pawl because parking brake not used). Nowadays, parking pawls are not nearly as tapered, nor are the gears they lock into. This is not ours, but, gives an idea of how they generally look nowadays.

They're generally spring activated, so, if the car is in park, and thinks it is, then the pawl retainer is disengaged and the spring yanks it into a geartooth valley.

7048



This is an earlier version of the one in the TR690

7050



2m10s mark:

  • FMVSS 114 – Theft Protection and Rollaway Prevention, Keyless Ignition Systems
  • SAE J2208 – Park Standard for Automatic Transmissions
 
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