1500 rolls down hill with brake on?

[af2018]

I might be missing something here, but my drive way is on a slight decline towards the road.

Yesterday i backed the 2018 truck up the driveway, didn't put on the parking brake, put it in 'park'... and it rolled slowly down the driveway!

now... in my experience, the regular brakes should be enough to prevent this, right?

there was a small amount of ice under the left tires.

is this normal? the tires actually 'spun' as the truck moved... the tires weren't stationary as the vehicle slid.

I've never had to apply the parking brake to any other vehicle to be sure it doesn't move. if i wasn't paying attention, it would have rolled right into traffic. i had to jump into the moving truck and hit the brake pedal.

shouldn't the regular brake be enough??
I've never heard of people applying the emergency brake EVERY single time they park.

 

[crash68]

Sounds like one of parking brakes isn't adjusted correctly or they're not working.
If you have the BW 44-44, then leaving the truck in 4X4 and setting the parking brake to brake all four wheels will not work with your transfer case. Without the truck running the front wheels disengage.
Using the parking brake with a part-time transfer case(BW 44-45) to lock all four wheels is a definite perk in some instances.

 

[troutspinner]

How far? an inch or so or a full tire revolution? Until the transmission hits the lock spot, wheels will move slightly. This goes for any automatic transmission.

 

[limited delmo]

Are you sure all the tires were turning or just the front? My guess is the rear tires were locked in park and sliding on the ice.

 

[muddy12]

Here s what I believe was happening(I’ve seen it before with icy conditions, mostly in 2wd’s with open differentials.

Truck was parked on an incline, and the transmission put in park. Parking brake was NOT applied.
The tires on one side of the truck were on ice which means they had very little traction.
Because of the differential in the axle, even though the trans is in park, once the tire on the ice slips, the tire on the other side will start to rotate.

Tires on the icy side were most likely spinning opposite of direction of movement.


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[Guyfromthenorth]

Here s what I believe was happening(I’ve seen it before with icy conditions, mostly in 2wd’s with open differentials.

Truck was parked on an incline, and the transmission put in park. Parking brake was NOT applied.
The tires on one side of the truck were on ice which means they had very little traction.
Because of the differential in the axle, even though the trans is in park, once the tire on the ice slips, the tire on the other side will start to rotate.

Tires on the icy side were most likely spinning opposite of direction of movement.


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x2 for this explanation. You can easily demonstrate this by hand if you jack both rear tires off the ground and leave the truck in park. You can turn one tire by hand freely and the opposite tire will turn in the opposite direction. This is normal action of the OPEN differential in the rear end.

This won't happen if:
-You have an automatic locker installed
-You have LSD installed and it's clutches aren't worn out
-You have the parking brakes on
-You have it parked in 4wd and the other tires have traction

Parking on ice with an open diff should be always done with the e-brake. This is also why people have vehicles roll off jackstands and sometimes kill themselves. They jack up on side of the rear end and as soon as the tire leaves the ground, and you're on even a slight incline, the truck will roll forward and off the jack or stand, hopefully you won't be under it when it happens. Apply...the...parking...brake lol.

 

[o2cmefly]

When you put an auto transmission in park, a small pin called a parking pawl holds the vehicle in place. it is NOT designed to hold it’s weight though. You should always apply the parking brake to prevent this pin from bending or breaking. This is exactly why FCA put an automatic parking brake on these trucks, and many of their other cars. This way, when you put the transmission in park, the brake is applied too.

https://en.m.wikipedia.org/wiki/Parking_pawl

“Most vehicle manufacturers[3] and auto mechanics[4] do not recommend using the transmission's parking pawl as the sole means of securing a parked vehicle, instead recommending it should only be engaged after first applying the vehicle's parking brake. Constant use of only the parking pawl, especially when parking on a steep incline, means that driveline components, and transmission internals, are kept constantly under stress, and can cause wear and eventual failure of the parking pawl or transmission linkage. The pawl might also fail or break if the vehicle is pushed with sufficient force, if the parking brake is not firmly engaged. Replacement can be an expensive operation since it not only requires removing the transmission from the vehicle, but it's usually the first component to be installed in the gearbox case during a complete rebuild.

It is highly inadvisable to use the parking pawl to stop a vehicle in motion. Modern parking pawls are connected to a safety mechanism that prevents the pawl from engaging unless the vehicle is stopped first. The pawl mechanism is generally not strong enough to stop a vehicle in motion, if it engages at all. Under that much stress, the pawl may simply break off in the transmission, leading to costly repairs.”

 

[af2018]

How far? an inch or so or a full tire revolution? Until the transmission hits the lock spot, wheels will move slightly. This goes for any automatic transmission.

it would have kept rolling down the entire hill had i not jumped in to slam on the foot brake

 

[af2018]

Are you sure all the tires were turning or just the front? My guess is the rear tires were locked in park and sliding on the ice.

thats what i thought, so i recorded the back tires with my camera on the ground and all 4 tires were actually turning

 

[af2018]

Here s what I believe was happening(I’ve seen it before with icy conditions, mostly in 2wd’s with open differentials.

Truck was parked on an incline, and the transmission put in park. Parking brake was NOT applied.
The tires on one side of the truck were on ice which means they had very little traction.
Because of the differential in the axle, even though the trans is in park, once the tire on the ice slips, the tire on the other side will start to rotate.

Tires on the icy side were most likely spinning opposite of direction of movement.


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thanks. you had me until you said 'most likely spinning opposite of direction of movement'. how would the tires spin backwards if the truck was rolling forward? from what i saw, the tires on ice were turning in the direction it normally would when driving forward.

actually... there is no ice today. ill go try it now and report back!

 

[af2018]

It is highly inadvisable to use the parking pawl to stop a vehicle in motion.

interesting! thanks! does your above quote mean that if/when the truck rolls, its advised to not slam on the foot brake?
..that you should push the parking brake with your foot instead?

i may be misreading this.

 

[muddy12]

thanks. you had me until you said 'most likely spinning opposite of direction of movement'. how would the tires spin backwards if the truck was rolling forward? from what i saw, the tires on ice were turning in the direction it normally would when driving forward.

actually... there is no ice today. ill go try it now and report back!

It’s because of the side and spider gears inside the differential.

I think it was mentioned already, but try this.
With the truck parked (transmission in park)on a flat level surface, and the front tires blocked, jack up the rear axle(both tires off the ground).
Now grab one tire and spin it. The other tire will be turning the opposite direction.

Once the tire on the ice lost traction, it was being driven(through the differential gears) by the tire that was not on the ice.


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[Graygoose]

http://www.safetyresearch.net/blog/articles/fca-launches-autopark-“customer-satisfaction-notification”-campaigns-why-no-recall


wasn't there a Jeep recall for popping 8 speeds out of gear?

 

[af2018]

It’s because of the side and spider gears inside the differential.

I think it was mentioned already, but try this.
With the truck parked (transmission in park)on a flat level surface, and the front tires blocked, jack up the rear axle(both tires off the ground).
Now grab one tire and spin it. The other tire will be turning the opposite direction.

Once the tire on the ice lost traction, it was being driven(through the differential gears) by the tire that was not on the ice.


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thanks for the explanation. i don't have the means to jack it up but i believe you. i can't visualize the two tires spinning in opposite directions though when they are touching the ground. it would be like sticking your finger in a moving hamster wheel.. won't turn.

 

[Guyfromthenorth]

thanks for the explanation. i don't have the means to jack it up but i believe you. i can't visualize the two tires spinning in opposite directions though when they are touching the ground. it would be like sticking your finger in a moving hamster wheel.. won't turn.

Pssst... that's where the ice comes into play. Ice=no traction.

Watch this:
Watch it. It starts sliding IN PARK. The front wheels are freewheeling which is normal. The back tire we see is sliding on ice and not moving but once it bumps the curb and gains traction it starts turning forward, if we could see the other side it would be turning backwards on the ice. Either that or he we have a clip of a truck....sliding on ice as normal....that suddenly has a transmission failure at exactly the same time for some reason....orrrrrrrr.....its how a differential works and thats why we have parking brakes.

 

[silver surfer]

interesting! thanks! does your above quote mean that if/when the truck rolls, its advised to not slam on the foot brake?
..that you should push the parking brake with your foot instead?

i may be misreading this.

No, he is saying if vehicle is in motion, don't shift transmission into park (if it not). Use foot brake or parking brake to stop vehicle, then shift to park. Shifting to park is what engages the "parking pawl" in the trans. Also, don't use Park alone to hold vehicle, especially on an incline. Use the parking/emergency brake.

 

[af2018]

Pssst... that's where the ice comes into play. Ice=no traction.

Watch this:
Watch it. It starts sliding IN PARK. The front wheels are freewheeling which is normal. The back tire we see is sliding on ice and not moving but once it bumps the curb and gains traction it starts turning forward, if we could see the other side it would be turning backwards on the ice. Either that or he we have a clip of a truck....sliding on ice as normal....that suddenly has a transmission failure at exactly the same time for some reason....orrrrrrrr.....its how a differential works and thats why we have parking brakes.

Wow. this totally explains it! you are a HERO! thanks.
thats exactly what happened to me.
SOOO... this would not have happened if the parking brake was on??

 

[Guyfromthenorth]

Wow. this totally explains it! you are a HERO! thanks.
thats exactly what happened to me.
SOOO... this would not have happened if the parking brake was on??

Exactly, the parking brake will lock both wheels which means neither one can counter-rotate, they would BOTH have to slip on ice to move the vehicle. I'm frequently working on trucks broken down on winter roads in the North up here. They are hardpacked white snow\ice roads with no sand\salt treatments. The safest way (other than not doing it at all) to jack up a truck on those conditions is: lock in 4x4, set the parking brake, apply wheel chocks, and finally have a spotter. Ice is more dangerous than most people give it credit for around vehicles.

 

[Jrod]

Happened to me the other day. Parked three wheels on ice on very slight incline. The trucks started sliding / rolling backwards as I opened the door. I quickly learned to start utilizing my E brake. Problem fixed.