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  #121  
Old 02-17-2014, 08:33 AM
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This thread is definitely way off topic.

Okay, so...in review, the OP of the thread was actually just noting that it is likely something did happen to his transmission as it does not seem to engage the parking pawl properly (more than once). That's an issue, and Jeep needs to look into it and determined what failed. Yes, he should have had the parking brake set, but his original post was not claiming anything to that effect--in fact he may have realized this error.

What seemed to set off the huge debate was another post from "Summit" that was claiming a similar incident and all sorts of dramatic statements about "fear for children" and that the vehicle "tried to commit vehicular homicide." It was a rather hyperbolic post that was ridiculous sounding in its drama as, while the vehicle may or may not have failed, proper USE of the available equipment would prevent the "fear" and "homicidal tendencies."

Here are the straight facts as we can set them out:

1) A JGC (or two or whatever) may have had a parking pawl, transmission, or linkage select failure of some sort, allowing it to roll in park much easier than it should be allowed to. This is either a defect or a failure of some sort.

2) The users of said vehicles were not properly using the parking brake. Proper use of this would have prevented the rolling, but the failure may still be an issue regardless.

3) The transmission parking pawl is basically a ratcheting pin arrangement which locks the gear train to the transmission case. It is NOT a large or heavy-duty mechanism. It is not recommended to rely on this to hold a vehicle in place. It will usually hold, but every time you put that much stress on it (especially with a vehicle of significant mass like the GC) you are taking a risk.

4) There's a backward conception about the parking pawl--and I've made the mistake of referring to it as the "primary" holding mechanism as well by habit. In reality, parking pawls were introduced into automatic transmissions (very early ones did not have this) as a SECONDARY holding method. The parking brake was (and still is) considered to be the PRIMARY holding mechanism in park, as with manual transmissions. The parking pawl was added as a safety mechanism (a backup) in case the parking brake failed or was not set. So whenever you're relying only on the parking pawl, you're relying on a backup mechanism only the (1) isn't especially good for the transmission and (2) isn't as strong as the parking brake.

5) If the parking pawl in these GCs isn't engaging or is broken, that should definitely be addressed as your secondary safety system isn't functional. It's a problem. No doubt.

6) Failures do happen. Don't rely on your secondary mechanisms alone.

7) SW03ES isn't a troll. I've disagreed with him on other topics before but he's always just been arguing his case from data on his side of things. Just because you can't change someone's mind doesn't make them a troll. He has some very valid reasons, that I agree with, for not allowing people to simply post statements that make it seem "okay" to not use the parking brake. It's negligent to not use it. No, you can't force people to use it, and shame on them if they don't. But allowing people to wander around feeling it's acceptable to not use it is also negligent if you know better. Someone knowing something that you don't (for whatever reason) shouldn't be a "threat" to you. It's more information for you. Use it. It isn't a contest to see who can race to the bottom and have no information.

8) I don't think anyone here can effectively argue that they shouldn't use the parking brake. May not want to, but not that they shouldn't. If you don't use it, and you have a failure (or even a design flaw!) you are negligent as well.

Group hug everyone. Or something.
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  #122  
Old 02-17-2014, 08:37 AM
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Re: Holy smacks! My JGC just moved itself out of the driveway

Not much I can add to that, sums it up perfectly...
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  #123  
Old 02-17-2014, 09:03 AM
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Re: Holy smacks! My JGC just moved itself out of the driveway

Arguing for the sake of arguing, for the enjoyment of it, to the annoyance of the community..... if that is not trolling, what is?

The parking brake violation in Texas is a not a felony or misdemeanor but is merely a civil infraction penalized by a $30 ticket. "Against the law" may not be the appropriate terminology. The penalty is less than that for failing to come to a complete stop at a stop sign. In some states (Mass. being one), parking violations do not even rise to the level of a civil infraction.
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  #124  
Old 02-17-2014, 09:10 AM
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Re: Holy smacks! My JGC just moved itself out of the driveway

On an unrelated matter...after you place your Jeep in Park, and remain in the car long enough for the dashboard lights to go out....does your e-shifter move or emits some noise ?
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  #125  
Old 02-17-2014, 09:21 AM
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Re: Holy smacks! My JGC just moved itself out of the driveway

Quote:
Originally Posted by f1anatic View Post
On an unrelated matter...after you place your Jeep in Park, and remain in the car long enough for the dashboard lights to go out....does your e-shifter move or emits some noise ?
Yes. If you leave your hand on top you can feel what seems like a relay. I noticed it, and mentioned it, when doing the first uConnect update, way back when.


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  #126  
Old 02-17-2014, 09:29 AM
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Re: Holy smacks! My JGC just moved itself out of the driveway

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Originally Posted by Rexlion View Post
Arguing for the sake of arguing, for the enjoyment of it, to the annoyance of the community..... if that is not trolling, what is?
Thats absolutely not what I was doing. Its an important topic, and I'm not going to let people tell others its okay to choose not to use the parking brake when I *know* that is not a safe way to operate a vehicle. I never said anything disparaging or insulting towards anybody (folks haven't been as kind to me but like I said, I'm a big boy), but like I said I'm not going to back down on this...its in the manuals for this vehicle and every other vehicle, its in drivers handbooks of at least 5 states that I could find from a simple google, its the law in at least one state, people's vehicles are rolling away endangering others as evidenced by this thread and other sources when Googled...its a big problem that the public at large doesn't understand the way the transmission and parking brake work together.

Everybody's entitled to an opinion, but not to their own facts. If you want to post some facts that say the parking brake is not necessary...post away. Nobody has done so. An omission in a two page getting started guide is not proof when that some manufacturer goes out of their way in multiple paragraphs in their full manual to make sure to warn everybody to NEVER use park as a substitute for the parking brake. If you look through a bunch of manuals as I have done during this thread you will see that Chrysler's warning is bolder and bigger than other manufacturer's warnings.

Quote:
The parking brake violation in Texas is a not a felony or misdemeanor but is merely a civil infraction penalized by a $30 ticket. "Against the law" may not be the appropriate terminology. The penalty is less than that for failing to come to a complete stop at a stop sign.
You're arguing semantics. If the law says you have to use the parking brake, not using it is AGAINST THE LAW. Bottom line. Whether something is a minor offense or not, its still against the law. Failing to come to a complete stop at a stop sign is against the law. Spitting on the street is against the law...etc etc. If they can write you a ticket its against the law.

Someone said its not against the law in the states, we showed that was not the case in every state. Accept it, its the facts.

Like Peter said, there is no effective argument that you should not use the parking brake. It makes everybody safer...I'll continue to post this until my fingers bleed if I have to.
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  #127  
Old 02-17-2014, 03:35 PM
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Re: Holy smacks! My JGC just moved itself out of the driveway

Update -- spoke with the dealer today. Service manager said there are no TSBs and they've not heard of it happening to others. Told him I'll share with them the posts on this group when I take it in here in the next couple weeks, and told him if I could replicate it again, I'd film it.

He was not questioning whether it happened, just I don't think they know what to do.

I'll wait on the next snow. Question for those of you out there familiar with how the differential and transmission may function.

If one of the tires were able to slide, when it was in park, would the JGC differential/transmission combo allow the other wheels to roll backward? Or am I just unfortunate enough that my parking pawl is malfunctioning?

I ask because it seems it doesn't do that when the driveway is dry. Of course, it didn't do it even before when it was snow-covered, until last Thursday.

Thank you.
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  #128  
Old 02-17-2014, 04:02 PM
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Re: Holy smacks! My JGC just moved itself out of the driveway

Mark the tires with a chalk, that will tell you if they rotated or it was a lack of grip.
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  #129  
Old 02-17-2014, 04:16 PM
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Re: Holy smacks! My JGC just moved itself out of the driveway

Quote:
Originally Posted by GoHerd View Post
Update -- spoke with the dealer today. Service manager said there are no TSBs and they've not heard of it happening to others.
Unfortunately thats a pretty standard dealer response in general...

Quote:
If one of the tires were able to slide, when it was in park, would the JGC differential/transmission combo allow the other wheels to roll backward? Or am I just unfortunate enough that my parking pawl is malfunctioning?
When you put it in park now, does the pawl hold? If it does then the pawl is obviously not broken. If the pawl were broken park would be like neutral.

The parking pawl keeps the driveline from moving...so any wheels not hooked up to that driveline are free to roll. So, in normal/shutdown mode that means the front wheels are free...

If you don't have an LSD, it may only be one wheel that is locked (thats what they were getting at when they were going to install an LSD on that Summit in the other thread). So, if the locked wheel is able to slide on the snow without turning, then yes the three other wheels would be able to move freely. The issue is that once you have momentum, if that locked wheel moves off the snow onto dry ground its enough to shove it off the pawl and then its just in neutral.

FYI: http://myautomatictransmission.com/t...kiing-pawl.htm

Quote:
In this article we will take a look at a device used in automatic transmissions to lock the transmission's output shaft when the shifter lever is in the Park "P" position so that the drive wheels cannot rotate.

What is a parking pawl?

A transmission parking pawl is a metal pin or lever that engages the transmission's output shaft when the transmission shifter lever is placed in the "Park" or "P" position. When the transmission pawl is engaged it restricts the output shaft (and drive wheels) from turning in either direction.parking pawl

Contrary to common thinking, the primary purpose of the transmission's "Park" position (and parking pawl) is to keep the engine's power from reaching the drive wheels when the engine is running, not to keep the vehicle from rolling when parked - this is the job of the parking brake (or e-brake). In fact, relying solely on the transmission's "Park" position and the parking pawl to keep the vehicle from moving when parked places undue stress on the parking pawl, which can lead to premature failure of the pawl. See Important Tip below.

Signs that your parking pawl is worn out or broken

If your vehicle rolls forward or backward an inch or two after placing the shifter in the Park position, the parking pawl is worn out and weak. If your vehicle rolls freely when the shifter lever is in the Park position the parking pawl is broken.

Parking on an inclineparking pawl

When parking on an incline, undue stress is placed on the parking pawl unless the e-brake is set before the shifter lever is moved to Park. If the shifter lever is placed in Park before setting the e-brake, the parking pawl is holding the weight of the vehicle, not the parking brake. Overtime, when the parking pawl is used in this way, it becomes weak and can break.

If the parking pawl fails while the vehicle is parked and unattended, the vehicle is free to roll as gravity dictates. This is why you should never rely solely on the transmission's Park position to secure a parked vehicle - always set the e-brake.

Replacing the parking pawl

Replacing a broken or worn out parking pawl requires opening up the transmission, which in most instances means removing the transmission from the vehicle. Replacing the parking pawl once the transmission case is opened up is not difficult. But removing the transmission and re-installing it is a sizable job. Automatic transmission removal do-it-yourself instructions.
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  #130  
Old 02-17-2014, 04:27 PM
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Re: Holy smacks! My JGC just moved itself out of the driveway

I pretty much always use the parking brake....just a habit. The other night, I was backing my car out of the garage, into my driveway (which has a slight slope). It was snowing and I wanted to grab a shovel out of the garage. I put the car in park but didn't apply the parking brake. Next thing I know, my Jeep is rolling down the driveway. I quickly jumped in and pushed the brake. I was shocked that it rolled while in park. I wasn't sure if it slipped in the snow, but that didn't seem likely.

Although I usually apply the parking brake, it was unsettling knowing this could happen.
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  #131  
Old 02-17-2014, 04:36 PM
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Re: Holy smacks! My JGC just moved itself out of the driveway

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Originally Posted by Dcbullets View Post
I put the car in park but didn't apply the parking brake. Next thing I know, my Jeep is rolling down the driveway. I quickly jumped in and pushed the brake. I was shocked that it rolled while in park. I wasn't sure if it slipped in the snow, but that didn't seem likely.
I bet its exactly what happened to the OP, the one wheel that is stopped by the parking pawl slid on the snowy driveway and started the vehicle in motion since the other wheels are free without the parking brake applied. Its a heavy vehicle, once its moving the pawl is going to pop right out...

Or the pawl may not have seated into the tooth all the way and just popped out.

Cars can absolutely slide down a snowy driveway. 3 or 4 years ago the Prius the Jeep replaced slid down my lightly sloped icy driveway at night even in park and with the parking brake applied. It didn't roll away, because the parking brake kept the rear wheels from turning at all and when the slide was over it just sat there at the bottom of the driveway...but had the brake not been applied it absolutely would have rolled out into the street.

Bear in mind with the Pawl, this is all we're talking about, you can see how a jerk or torque of that output shaft could very easily pop the pawl off the tooth...and you're in neutral:

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  #132  
Old 02-17-2014, 04:43 PM
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Incline + icy = bad place for parking a vehicle. Neither the parking pawl or the parking brake will hold in that situation.

Here's something interesting. Why does it not slide right away? That's a cool answer...and generally applies to the vehicle right after you stop in those conditions. It seems to be held firm. You get out...do something, and next thing you know it's rolling (sliding) away. The answer is your tires. They have residual heat. They start to melt the snow/ice and form a water layer over re-freezing water right below that. The coefficient of static friction drops and suddenly...wheee...
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