Hmmmm? So I have a new 2019 3500HD Denali with the 6.6L Duramax Diesel motor and Allison transmission. Same issue of rolling backwards. I got home the other night about a week and half ago from grocery shopping. Parked the truck on my inclined driveway to unload groceries. I KNOW it was in park, and the motor was turned off....as I had the keys in my pocket. I opened the back door, brought a load of groceries in the house and set them down, came back out and the truck was in the street! Thinking that "maybe" I didn't get the truck in park properly (even though I an engineer with a graduate business degree, in my mid 50s, and NOT insane), I got in the truck, started it, and pulled it back to the original parking location in my driveway. I check at least 3 times to ensure the stick shift was in fact in PARK. It WAS! So I turn off the motor, get out, shut the door and grab some more groceries from the back seat. As I walk away from the truck I hear a "click"/"pop" sound, and I turn to see the truck rolling backwards into the street again!!!! It was "lurching" backwards as it appeared some mechanism was attempting to engage to stop it. It was not a smooth roll. Eventually, that something engaged, and the truck stopped......in the street which is flatter. I had something similar the first month I bought the truck in May of 2019, where it only rolled back about 1 or 2 feet. For that, I though maybe I just parked it in the wrong spot, not pulling in as far as I normally do. Those of you who park cars in a driveway location know that probably park within 1 inch of your normal location. Anyway......each time this happened, it was very cold outside - perhaps 20 degrees F, or colder. This latest time, I had just driven the truck, so the tranny and engine were warm when it happened. The dealer (Alpine GMC in Denver area) just looked at it, and could find any issues or bulletins. I would encourage others to write and document.......cause someone is going to get killed with this issue! Had there been a kid behind the parked truck playing in the day, or had someone been walking on the sidewalk, they would have been rolled over! The Service tech at the dealer informed me when I called in that just had another guy with the same issue in the shop. But his truck was the 1500 and gas motor with a different transmission. There WAS a service bulletin on his, but doesn't apply to my model. In the meantime, I will be consistently using my parking break! Eventually, someone will be killed and lawsuit filed. GM needs to resolve this!
