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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.

View attachment 7048

This is an earlier version of the one in the TR690

View attachment 7050


2m10s mark:

  • FMVSS 114 – Theft Protection and Rollaway Prevention, Keyless Ignition Systems
  • SAE J2208 – Park Standard for Automatic Transmissions
Older designs were definitely easier to bounce over the teeth which had narrower shoulders and more slope.

Does the Ascent have direct cable or lever engagement or solenoid actuated pawl? A solenoid failure would explain not really engaging park.
 

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Older designs were definitely easier to bounce over the teeth which had narrower shoulders and more slope.

Does the Ascent have direct cable or lever engagement or solenoid actuated pawl? A solenoid failure would explain not really engaging park.
Control of the TR690 drive modes is done by the shifter select cable (from the shift lever) to the shift arm on the transfer case. The parking pawl on our TR690 still has an actuator rod and return spring, like most others. Our service manual would indicate it is a physical mechanism that engages it. The transmission shifter arm and inhibitor switch are mounted to the CVT (transfer case, technically), and are not on the shift lever in the car.

The inhibitor switch does a LOT more than what its name sounds like. It has a 30 pole harness, and controls letting the TCM know when the car is in any drive, neutral or park range, controls the starter signal, by sending Park or Neutral data to it, and also controls sending the signal to the reverse/"back-up light" circuit. It's fixed to the CVT case, so, if the car turned off and thought it was off, it's almost always because the CVT (the mechanical shift lever on the transfer case) was mechanically in Park. Alternatively, there's the rare case that the inhibitor switch/cable moved or needs adjustment - but in that case, Drive, Reverse and Neutral generally don't work either.

There are two bolts that hold it - it's usually the last place of fault, from what I've seen (and that's usually because it was messed with). You can see the two bolts on the right side of the image that hold the inhibitor switch assembly (the shifter select rod (A) goes through it.

7054


This guy shows how it works on a Ford transmission, which is pretty much the typical setup.
 

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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. View attachment 7047
Urban development is often recommended 1-3% slope driveway. That slope, I think, is about 10-30%.
 

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Any chance tires were warm and it did an ice slide, like the rocks on the racetrack in death valley ?
Precisely what happened to my old crew cab Silverado several years ago. Backed into a parking space on the top level of a snow covered parking garage. Truck was on a slight side slope, being an “up” ramp of the garage. Came out a couple hours later only to discover that the (heavier) front of the truck had slid down the slope, almost completely perpendicular to the original position!

A cursory look at the photos here... I see what looks like snow “forced” out of the tire tracks, which to me indicates that it may have been sliding rather than rolling. And, the damage also looks so minimal that it leads me to think that it was a pretty low-speed impact with the tree... also indicative of a slide, as opposed to a runaway roll.
 

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Wow, great point, guys. I remember driving my e350 one day when they hadn't sanded the NY440 bridge near the Outerbridge Crossing, and I literally stopped on the top, it slid sideways until both passenger side wheels were leaning against the curb. I got out and could push the van off the curb with one hand, easily. The Bridget's lateral lean was that little, and the snow and ice was that slick that it was that easy to move a 10,990 pound GVWR county bus van.

I rubbed my tires down the curb the entire way down to help prevent momentum.
 

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Years back, on an icy morning and dusting of snow a bunch of us parked as usual in the parking lot across from my old high school and went to class. When we went out later, every car had slid to a new spot. Some against the poles, most into each other. I luckily had just slid back about 20’ and ended up nearly sideways beside but not touching my friends cars that did the same thing. The lot was nearly level and flat, just enough slope for drainage. Nobody had touched the cars, a few people watched them slide and later there were videos on the news showing it happen in other lots around town.
 

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That (above in the preceding posts) would explain the tire tracks, and the minimal damage. I suspect if the car was a runaway (free rolling down the hill), I'd expect a lot more damage. 4,600 pounds (plus) hitting the aluminum hood on a free roll on that slope would probably crunch it and the headlight pretty badly - and likely the fender.
 

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I’ve seen this before on a few manuf. vehicles. As ice forms on the paved surface, the weight of the car, etc etc.... park+emergency brake, they can just slide on down an incline. I think turning your wheel in a side direction might prevent it from floating away down an incline!
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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I’ve seen this before on a few manuf. vehicles. As ice forms on the paved surface, the weight of the car, etc etc.... park+emergency brake, they can just slide on down an incline. I think turning your wheel in a side direction might prevent it from floating away down an incline!
which is one reason I had always been taught decades ago to park with the wheels turned into the curb.
 

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Don't know if this is totally applicable in the case of Subie AWD, but in a standard 2wd open diff rear axle, all it takes is for one of the rear wheels to be able to slip and the parking pawl is useless; the wheel with traction will spin in the direction of travel, but the slipping wheel can spin backward, allowing the vehicle to move even though in park. Have had it happen when parking a vehicle next to the curb where the street is clear and the snow melt running next to the curb has frozen to ice. If the transfer case (for lack of a better term) between our front and rear axles doesn't lock together when the car is off (I don't if this is the case) and the front and rear axles both work essentially like a traditional open differentials, then two sliding wheels would be enough to let the car move down the hill. Will be really interested to hear the explanation for this one...
 

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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.
Did you end up reporting this to Subaru? Just curious on what they had said.
 

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If the sliding theory is correct, is this a situation that All Season M+S tires are prone to and switching over to snow tires would prevent? What about if the tires were wearing cables or cable links? Would these measures prevent such sliding?

BTW, this is a great discussion with all the sleuthing going on. I feel bad for the owner who posted the original problem, but there is value in considering all that has been posted.

I remember a time (decades ago) when I pulled my Toyota SR5 to the shoulder of Hwy 41 (just north of Oakhurst, CA) because the sign said "chains required." I wasn't sliding up to that point. But while waiting for a safe opportunity to open my door, the truck started to slide sideways towards the 8 o'clock direction, right in front of oncoming down-hill traffic. Fortunately, no collision, because the downhill traffic already had on their chains and were driving slowish enough. But my driver's side wheels were off the pavement and the door was pinned up against the embankment. Crazy to think about how I actually got the chains on the passenger side, backed it down-hill just enough to get the chains on the other tire and somehow managed to get going again.
 
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