I have a 04 base model Silverado V-6 5 spd. It spits and sputters going up thru the gears, I get into 5th and it seems to run fine. Just had a tune up a few hundred miles ago. Need help, I don't want to tear up the drivetrain.

 

If a repair shop did your tune-up take it back and have them look at it again.

I'll bet the problem is still there in 5th gear - seeing that you're not accelerating it is not nearly as pronounced as it is under a load.

It really sounds like a cylinder misfire which could be anything from a small piece of carbon on the plug electrode to a dead cylinder.

 

You are correct about the issue still being there in 5th gear. I noticed this morning on my way to work. I also noticed under hard acceleration it doesn't seem like it's there or not. If it is I can't notice it.

 

Are you throwing any service engine codes ?