my 2010 f150 was parked on a very slight grade overnight. This morning it has slipped backwards to the end of the driveway about 8 feet from where it was parked. It was in park and park brake NOT applied. Any ideas?

 

Do you have teenage kids???

Kidding aside, I have no idea how a truck would move several feet on its own.

 

Wow, haven't heard of this in ages. We used to call it creeping and was associated with certain transmission and was actually sort of normal. My 86 Nissan would creep about 1 - 3" an hour backward out of our driveway and we never found anything mechanically wrong with it. I had it 10 years or so without a breakdown. It could also be caused by something going wrong in the transmission as well though.

You might want to make sure that it actually is happening without someones help and then take it to get checked.

 

Suspect that the coefficient of friction between the tires and the surface that they were on wasn't sufficient enough to hold the vehicle in place.
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No joke my last truck did this, but the driveway had a small layer of snow and it was frozen, my truck slid down 4 feet sort of following the tracks I drove in on.

It freaked me out in the morning but I realised it had slid after looking.

 

My only suggestion is to use the parking brake.

 

Just a thought, but if you have an open differential, or even a weak limited slip, only one tire has to slip for the truck to move, while in park. The other will simply roll along, because the driveshaft is locked. Was one side of the truck on slippery ground?


I've seen this creeping many times in manual transmissions, due to parking in too high a gear, or low compression, where it actually turns the engine, but in an automatic, there is a pawl in the transmission that locks the drum. If it's not functioning, the truck would completely free-wheel, like in neutral. Maybe it's the Carbonaro Effect!!!