2015 Gmc sierra

[alphaman]

Coming from driving a staight v8 to a vehicle with fuel saver tech. It's different!!
If you havent drivin a vehicle with the fuel saver technology. That could be the problem. I have a hemi and depending on how light or hard you press the gas. A certain rpm range (1000-2000 rpm) activates it which causes the engine to keep switching etc. My hemi has a slight vibration like bc Of that. If I put it in 5th gear which deactivates fuel saver tech. And it doesn't do that.

Try that keep it in 5 gear and see If it still vibrates. The put it in drive which activates the cylinder shut off and check again.