Every once in awhile (seems to being happening more lately) when I'm going down the road the rpms will drop and the go back up. It does not do this as it idles only when in gear and seems to happen at about 2500 rpm or so. I have tried different grades of gas and different brands it does not matter they all do the same thing.
So could the plugs be going bad and cause this? Could the Throttle body need cleaning? The truck has less then 40K on it so I'm stump and wondering where to start at. Ive checked the air filter and the stealership just did an oil change a thousand miles or less when it was it in to have the radiator replaced.

Thanks

 

Check your trans fluid. I bet you are a quart low. You just had your radiator replaced and I bet they did not top off the trans fluid lost when they replaced it. Been there done that.

 

I agree - you are probably low on transmission fluid. I had the same problem with my 2006 Hummer H3 - surging while driving - idle drops when stopping. I added transmission fluid - problem resolved.

 

As nice as it is that you were eager to respond this thread is literally a decade pass lol. I'm certain the OP is long since moved on to another item of concern.

 

We have another Winner of the Dug UP An OLD AZZED THREAD AWARD! READ: Old Threads/'Necro-Bumping'