My D/A truck moved overnight!?!?!?

[Quack_Addict]

2006 2500HD, Duramax / Allison, ~54k miles on it.
It's been parked for about a week without being started or driven. I had it pulled up where the chin spoiler was almost touching the mounting bracket of a snow plow for another truck. The concrete pad where the truck is parked has a slight amount of angle to it - nothing radical - just enough to facilitate draining of the pad when it rains.

This morning I was on my way out the door and noticed there was about a 3' gap between the front of the truck and the snow plow. I know I didn't start or move the truck, so I asked my wife (who never uses the truck) if for some reason she had moved it. Nope. The only option is that the truck somehow moved rearward that distance as the plow it was parked against can't be moved forward (the plow scoop is right against my garage door).

Any ideas what may have happened here? Only thing I can think of is maybe the park pawl in the transmission slipped somehow and let the truck roll backwards on the slight incline?

[DmaxMaverick]

If there was snow on the ground when you parked it, the snow may have melted or otherwise shifted, allowing it to roll a little. If the surface was bare, the pitch of the slab may not have been enough to roll it into park at the time, but time and some force (someone leaning on it, wind, temperature changes, etc.) may have caused a roll. The parking pawl on the Allison is very large, with a significantly greater spaced index, compared to other light truck trannies. A roll of 4" or more is not uncommon after it is placed in park and a roll is allowed to engage the parking pawl.

If none of the above is possible, you may have to call an exorcist.

[Quack_Addict]

There was up to an inch of ice under the back tires when I parked the truck last week. The ice has since melted and the truck is now sitting with all 4 tires on concrete. I was outside with my son on Tuesday afternoon and the ice was gone then, and the truck was still nosed up against the plow. I get what you're saying about the park pawl, but I can't imagine the truck rolling back an honest 3' (36") before the pawl engaged. FWIW, I have been parking the truck in the same spot for almost 5 years (rain, snow, shine) and it's never done this before.

I'm still scratching my head over this. Honestly, I'm a bit concerned. I never considered a parked vehicle like this a hazard, but as much as it moved it could have done some damage if another vehicle was parked close behind, or a kid...

[DmaxMaverick]

3 FEET??? OK. I read 3 inches before. My mistake.

Different scenario. I'd suspect the ice you parked on allowed it to slide downhill as it was melting. The ice under the tires melts slower, leaving a "pad" of ice stuck to the tires, which can slide very easily on the concrete. This would be a more acceptable and common occurrence. Seen it many times, and once a car slid nearly a quarter mile before crashing into a house.

There are a couple things you can do prevent this. Leave it in 4x4 when parked. Having all 4 wheels engaged may help prevent a slide. Chock the wheels. Move to a warmer climate.

[Mark Rinker]

Unless you parked the truck after some freezing rain event that had coated the surface in ice - no way it rolled or slid 3' while in PARK, unless you have a mechanical defect in the transmission.

Snow really isn't all that slippery once packed, and the weight of the vehicle will melt its way to tar if you park on 1/4" or less. Cars just don't move around on snow. Period. If this was common when parked on snow or ice, here in Minnesota we'd have cars crashing into each other all winter long...vehicles stacked like cordwood on dealer lots after snowstorms, etc.

How old is your son? ;) Any chance he he just experienced his first joy ride, and didn't bother to measure the distance between truck and plow...???

[87max]

better call Dr. Peter Venkmen.

[Quack_Addict]

How old is your son? ;) Any chance he he just experienced his first joy ride, and didn't bother to measure the distance between truck and plow...???


lol - my son will be 4 this summer. The biggest thing he's driven so far is his 6v powered John Deer tractor ;)

As of this morning, the truck was still parked where I left it yesterday morning, after moving it back up onto the concrete pad.

[More Power]

I remember an Allison tidbit from more than 10 years ago that said the parking pawl was rated for a 26,000-lb load. During our tests of the first D/A prototypes in October of 1999, a GM rep slammed the gear shifter into park while underway at a moderate 20-mph, to demonstrate how durable the pawl was (or maybe how testers test stuff that's that not theirs :o).

It made a loud and alarming ratcheting sound, but didn't flinch otherwise...

Jim

[Kennedy]

In my teen years I had a '69 Buick and parked in a lot to go goof off with some buddies. When I came back it was parked in the wrong spot in a relatively flat lot. Also had no park after that. Apparently the prank was to drag it off it's spot...

The Allison park pawl is one badass piece. It did not give.

[Mark Rinker]

File this one under 'CCE'. (Crop Circles, etc...) :D

[Kennedy]

More than once I have put a truck into Park on the dyno while teh wheels were still turning. The pawl is nicely rounded so it won't snag or wear, it just rattles until you stop and it can fall in.