Acceleration Issue

[jmontz32]

I have a 14' Sierra SLT 4x4 with 11,500 miles and 305 hrs on it. Last week i drove my truck on a 500 mile round trip to the beach and experienced several issue where my truck was seriously struggling to accelerate, and I am not talking 0-60 acceleration, I am talking accelerating from a stop sign going 0-10 and switching traffic in lanes. It was not anything in my head because everyone in the truck felt it then, almost like a violent jolt, and it has continued to do it sporadically since. To describe what it feels like, it almost is like the grad braking system is violently engaging when i accelerate or the truck is switching into 4 WD. (I know that these two things are not happening, I'm just trying to give an example of what the issue feels like). For it being a 4wd with the 3.42 axle it did extremely well in my opinion averaging almost 21 mpg highway to and from the beach, but this truck is only 6 months old and to be experiencing a problem like this i really am highly concerned. With my luck i will bring it into the dealership and it won't do it when they test drive it. Anyone have any idea what could be going on?