2500HD won't slow down while driving
 

I have a 2004 2500hd 6.0l gas motor when I am driving it and let off the gas petal it feels like it is going to start slowing down but it doesn't. Almost feels like inset the cruise control it just says at the same speed I can use the breaks to slow down and it will without trying to accelerate . When I stop and stay at idle everything g is fine. No codes and does not feel like a transmission issue thanks for your help

Just press the brakes.