My Mustang reverses itself out of the driveway overnight.

Norm Peterson

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I think a better description than "My driveway isn't very steep" is in order before this goes much further. I've had a car creep about one car length down a slope over the time it took to eat lunch (different car, MT, P-brake not set).

Engine compression and ring friction both contribute to an engine's capability for resisting the car rolling in gear (engine off). Consider the two together to be an "engine braking torque", where the friction is more or less constant but the compression of air in the cylinders is not. If the static friction component isn't enough to hold the car still you're left counting on compression - which can and will leak down whether the car is moving or not. If/when it leaks down low enough, the car will roll slightly until the next cylinder in the compression stroke sequence starts adding its compression resistance. The cycle can repeat, with the car doing a jerky little start-stop creep downhill.

Transmission gearing matters - the lower the gear the more effective the engine is as a P-brake. Reverse may or may not be a better choice (the ratio still matters, but the reverse gear profiles may not offer as much friction as the forward gear helical gears do). Same goes for axle gears, so if you've got 3.15's you're not in as good of a situation as an otherwise identical car with 3.73's would be.

Car weight matters - are you needlessly carting around any heavy stuff?

Tires have a little influence (tires that are taller than stock or of much lower rolling resistance putting you at a disadvantage here).


Norm
 
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drive_55_not

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I think a better description than "My driveway isn't very steep" is in order before this goes much further. I've had a car creep about one car length down a slope over the time it took to eat lunch (different car, MT, P-brake not set).


Car weight matters - are you needlessly carting around any heavy stuff?

Tires have a little influence (tires that are taller than stock or of much lower rolling resistance putting you at a disadvantage here).


Norm

I had an old wornout K5 Blazer back in my broke dick redneck daze stationed up in Virginia ... If I parked that rig on any real incline it would start lurching as soon as I got out and shut the door.

It sounded kinda like an old steam locomotive in the movies, krumpth, krumth, krumpth ..... the steeper the incline, the faster it rolled.

I carried a couple wheel chocks and threw em' under the tires when on pavement, When out in the woods I'd back it into a tree or park it with the tires in a ditch.

As for parking with the tranny in reverse, all that's going to do is turn the motor backwards when it starts moving ...

.
 

46addict

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The e-brake cable tension can easily be adjusted by tilting the center console up from the back end and tightening a tension bolt. Loosening the console just involves removing 2 bolts (or 4, can't recall offhand) on the floor of the console and then removing the two plastic bezels that surround the radio/climate control panel, then tilting the console assembly forward.

Mine has loosened up over time, as you feared would happen to you but it's not a big deal because adjusting tension is simple.
 

Wes06

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I had an old wornout K5 Blazer back in my broke dick redneck daze stationed up in Virginia ... If I parked that rig on any real incline it would start lurching as soon as I got out and shut the door.

It sounded kinda like an old steam locomotive in the movies, krumpth, krumth, krumpth ..... the steeper the incline, the faster it rolled.

I carried a couple wheel chocks and threw em' under the tires when on pavement, When out in the woods I'd back it into a tree or park it with the tires in a ditch.

As for parking with the tranny in reverse, all that's going to do is turn the motor backwards when it starts moving ...

.

But if it's tail first down hill. Wouldn't 1st Turn the motor backwards when rolling
 

mavisky

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1. Pull the ebrake handle fully. The cable is adjustable if you wear it out.

2. As mentioned. Put vehicle in gear and push it and see just how hard it is to push it.
 

06JET

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My 2 cents:
Go buy you some BEER or whatever you like to drink while relaxing. Take your car to a steep incline (at least more than your driveway). Pop the hood, stand in front of the car and watch the belts. If they turn while it backs down the road then it's your valves not seating or your rings not holding compression or maybe a bad head gasket, ect. Listen for odd noises and where they are coming from. If your belts are not turning while it goes down the road it's your clutch not holding. I have 5 kids so if it was mine I would have told them to push it while I look and listen. You may not have that luxury. I would have done this before I ever asked the question on this forum. Usually the guys here are just as eager to find out what is wrong as you are so they throw out ideas and wait for the final thing that fixed it so they can help others with a similar issues. Be willing to check things and give feed back about the results. Good Luck
 
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05stroker

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My 2 cents:
Go buy you some BEER or whatever you like to drink while relaxing. Take your car to a steep incline (at least more than your driveway). Pop the hood, stand in front of the car and watch the belts. If they turn while it backs down the road then it's your valves not seating or your rings not holding compression or maybe a bad head gasket, ect. Listen for odd noises and where they are coming from. If your belts are not turning while it goes down the road it's your clutch not holding. I have 5 kids so if it was mine I would have told them to push it while I look and listen. You may not have that luxury. I would have done this before I ever asked the question on this forum. Usually the guys here are just as eager to find out what is wrong as you are so they throw out ideas and wait for the final thing that fixed it so they can help others with a similar issues. Be willing to check things and give feed back about the results. Good Luck

5 kids, holy shit, you know what my advise is to you? Haha

Just messing with ya, good times.
 
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46addict

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5 kids, holy shit, you know what my advise is to you? Haha

Just messing with ya, good times.��
More tax deductions are a good thing. :insane:

My wife's PT cruiser with the 5 speed does the same thing. 135k miles on the engine. Parked in 1st gear, nose facing upward on an incline. It creeps backward a few inches, stops, then creeps some more. I guess the engine is letting out compression in one cylinder then relieving compression in the next cylinders and eventually the car will coast away if the incline is long enough. :smiley-face-popcorn
 

RED09GT

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OP, Let me get this straight, you'd rather have your car roll away into something or roll out into the middle of the street than risk putting a bit of wear on an adjustable cable?

Help us understand why that is.
 

07 Boss

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If someone could give me an answer as to why my car moves against the selected gear, that would be great. I don't know if this is a common problem or not. If I need to find a replacement 4.6 on Craigslist or something, what kind of money am I looking at? At the very least I'd like to perform an OE comparable rebuild and just drive my car as is in the meantime.

To make things clear: I'm not asking for a solution to keep my car from backing out. I can buy a chock for 5 bucks and I can pull my ebrake all the way up. I'd like to know why my car can't hold itself in gear without an ebrake or chock.

Thanks all!


Simple answer, your driveway is too steep to have the motor alone hold it. Simple physics, one force overcomes the other.

I'm a little confused as to why you would look at buying or rebuilding a motor before you would buy or replace a brake cable? That just seems a little backwards to me.

Whomever told you that taking these engines to the limit is bad for them is completely correct. But taking any motor to it's limit is bad for them. With that said, lugging it around at low RPM's in a tall gear is going to put more stress on motor parts than a shorter gear with higher RPM's. These engines like RPM's. Operating them in the right efficiency range is the best option.

My car sees or gets close to redline every day for the last 9 years, the last 5-6 at 485 rwhp. Take care of your motor and you won't have issues. I see more issues with trying to baby it around than letting her breathe. Just saying, I drive my car like it was stolen and she treats me just fine.
 

Norm Peterson

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For whatever reason, I think this 'rolling downhill' was new to OP and he has other evidence that his car's engine may have low compression (unspecified rate of oil usage). IOW, this topic could be intended as much for diagnosing engine condition than about what needs to be done better now to keep it parked in the same place on a slope.


Spinks - personally, I don't think I'd want to use a P-brake in "just yank hard on the lever until it don't go up any more" fashion either (I live in flatland USA and rarely use the P-brake on any car). You only need to pull it up enough to hold the car still. Find out where that is. Maybe one more click than what you've been using would be enough.


Norm
 
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tjm73

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I blame gremlins.

latest
 

Bingo

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A caution with the handbrake, however: that shit does freeze up. I stopped using the handbrake unless I'm on a considerably steep incline. I know it only freezes when it's obviously below freezing and there's water present, but I feel keeping it in gear alone on generally flat surfaces is safe.
 

tjm73

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Not using the hand brake will also lead to it to seizing.
 

skwerl

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"The bad news is that your car was totaled when the garbage truck hit it. The good news is that your parking brake cable is in absolutely pristine condition."
 

bujeezus

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"The bad news is that your car was totaled when the garbage truck hit it. The good news is that your parking brake cable is in absolutely pristine condition."

Hahahhahaaaa!!! Thanks Brian, I needed the laugh, especially tonite.
 

Rapture

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A caution with the handbrake, however: that shit does freeze up. I stopped using the handbrake unless I'm on a considerably steep incline. I know it only freezes when it's obviously below freezing and there's water present, but I feel keeping it in gear alone on generally flat surfaces is safe.


My parking brake cable seized up in the summer in California. Had to disconnect it to get home.
 

groundpounder

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My parking brake cable seized up in the summer in California. Had to disconnect it to get home.

This one time, at band camp................ ;)

I mean seriously, because something once happened to you does not make a probability of it happening again. I live in hot dry Nevada and set not only my MT 2007's e-brake everytime but also my e-brake on my 05 F350 and she sets her e-brake on her MT SE-R Spec V religiously. Never have we had a problem with an e-brake failing to disengage. Maybe we're special and the underpants knomes leave us alone because profits.
 
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Kuplex

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The e-brake cable tension can easily be adjusted by tilting the center console up from the back end and tightening a tension bolt. Loosening the console just involves removing 2 bolts (or 4, can't recall offhand) on the floor of the console and then removing the two plastic bezels that surround the radio/climate control panel, then tilting the console assembly forward.

Mine has loosened up over time, as you feared would happen to you but it's not a big deal because adjusting tension is simple.
Don't even need to go that far. Open center console. Remove access panel. Tighten/loosen.
 
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