Interesting: truck creeping down grade
SCOUT5
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My truck moved forward (down hill) over night and was about 3/4 to a full truck length from where it was parked yesterday afternoon. Total about 18 hours time. 2005 F150 fwd.
Seems the differential can allow this. With a little evaluation this morning I arrived at this. One wheel was sitting on a really slick slab of ice and the other on pavement. The drive has some grade to it. As gravity worked on it the wheel on the pavement had enough traction and torque to cause the other wheel to slip (turning backward actually) on the ice allowing the vehicle to move down hill.
This morning my son noticed the truck had moved. I went out to check and it was in park, not in fwd. I told my son "let's figure this out". First I backed the truck up the grade to where it was and placed a stick on top of the driver side tire. In 20 minutes the truck and moved forward six to eight inches as evidenced by the position of the stick. I thought "well wait a minute" that tells us the truck moved but not why or how. So I had my son placed sticks on the top center of both tires the drivers side was on pavement and the passenger side was on ice. After 20 minutes or so the truck had creeped forward another eight inches or so. This time, as evidenced by the position of the sticks,we could see the wheel on the pavement had turned forward but the wheel in the ice had turned backward.
My son then backed the truck up the grade (steeper actually) until both tires were on the pavement, put it on park and placed sticks on the top center of both rear tires. It's been three hours with no movement. with neither wheel being able to slip they hold each other steady.
Interesting, I did not know the differential could do that but when I think about it it's easy enough to see how it does.
Conclusion, setting the parking brake is a really good idea as is my habit of turning the wheel into a curb, into to or across any grade if possible. Given a steep enough grade this could happen in conditions other than ice.
Comments
Yep, that'll do it. With an open differential, you effectively have driving traction or compression braking traction on only one wheel. The same for trucks that have a driveline brake for an emergency brake.
I am always surprised at how many people DO NOT use their parking brake. I'm a stickler for it. In fact, I always make a habit of:
Neurotic? Probably. I'm not a mechanic, but I just don't like the transmission holding the load, or having to wrestle the shifter out of PARK later.
That's the way I've always done it. When you live in the hills of Tennessee either use that parking brake or put the wheel against the curb.
I always use the parking break when I park on an incline or when I park with a tow. Someday I hope my transmission will thank me.
Interesting thread. Wondering if my F250 will roll with the locking rear end engaged Detroit locker
i watched my truck work its way out a long dirt driveway once. it was many years ago during hurricane andrew. standard shift and i had left it in gear without the brake set. storm calmed down enough during the "eye" for me to get outside and set the brake.
OR!!
I would bet your clutch was slipping. Glazed flywheel and glazed pressure plate will do that.
Joe
Glazed as in donuts ?
my wife uses the parking brake every time she get out of a vehicle
I am the opposite I do not remember the last time I ever used one but then I do not live or park on a hill . but on ice even if the brakes were on transmission in park gravity could still allow the vehicle to slide down on ice ,
not I am against trying to be safe and see the point of doing it
I saw an old grain truck leave w/o a driver once. Engine was about shot and as the load increased, gravity caused the engine to slowly roll over and over allowing the truck to just 'snortle' down the hill. Fortunately, it rolled into the field rather than staying on the harder field edge and stopped on it's own.
Parking brakes are kind of like old people's muscles. If you don't use them, you will lose them. This is especially true here where I live where the winter roadways make your vehicle white as snow with all of the road salt used.
I had a very hair curling adventure this past Sunday aboard my Kubota tractor with the attached front end snow blower and rear end salt spreader. My very long, steep asphalt driveway needed salting and starting at the top of the hill with the blower down in slow 4x4 mode I began salting. Then I found myself totally out of control sliding down that hill with a curve coming up!! I avoided braking and did have a bit of fishtail going on but fortunately got control back at the bottom just before coming to the roadway. All happened so fast, about all I can remember are the prayers I was screaming on the way down!
After a change of underwear and a few days of thinking, might just be time to start closing up the place during winter months and becoming a snowbird!
Or get a set of chains for the Kubota!
Without using the parking brake, the clutch assy is the only thing holding the truck. The clutch will still function pretty much normally until you park it on an incline, floor the accelerator in gear, then the slippage will show up.
"Then I found myself totally out of control sliding down that hill with a curve coming up!! "
They make these things called 'tire chains' which often prevent such occurrences. Will also help you get back up that hill you just slid down.
OK! I called my Kubota dealer this morning and ordered a set of chains for my rear tires. Telling the gal my story on the phone had her laughing for several minutes. Her giggles got me started and between the two of us it was at least 5 minutes before she got composed enough to get digging into her computer for correct parts.😁
I got all of the pertinent info needed from her and ordered the chains. She then warned me that they would be pretty hard on my asphalt driveway. I said ya! I've made it these past 6 winters without chains but after what happened to me last Sunday, you only get KILLED once in your life! So I'm good with chains.
We then spent another 5 minutes laughing our * off! 🤣