[LEEVON]

The 8-speed is a different animal, I hope they can help you. Be glad you didn't buy the factory vibration that GM has no clue how to fix. My 17 Sierra has been somewhat disappointing and is about to get the boot before 3,000 miles. I can't stand the vibration and there is no fix in sight. I also have a bad shudder on deceleration and the cabin is so cramped. Also my seat is already wrinkling on the outer edge and it's not comfortable, I feel like I'm sitting on a fat wallet on each butt cheek. And I'm sitting completely upright, it's got less room than any regular cab I've owned from the 40's and up.

I am very jealous of your mileage, I'm at 15.6 combined highway/city and it's a regular cab 2wd 5.3/6 speed. It should do much better, otherwise why do I have to have all of this direct injection? Make sure you're getting all of this documented!