I got a 2000 Chevy silverado with 260k miles on it. The engine shudders slightly in idle intermittently, when traveling above 40mph up to 55mph the gears change and the engine begins shuddering if pressing the accelerator. The speed will slowly creep up but the RPMs do not climb when lightly pressing the accelerator unless you press down on the accelerator further and it drops gears. I had my spark plugs and wires changed only about 5000 miles ago. Recently had a new radiator placed along with hoses/fan.
There are no engine codes.
I'd try cleaning the throttle body and the MAF sensor, if those get dirty they can really affect the smoothness of the engine. Do that first, maybe check the air filter, and if that doesn't change much then I'd have a good mechanic with a high-level scan tool check the live data.
Here's Scotty's video for cleaning throttle body and MAF sensor:
https://www.youtube.com/watch?v=NWCKvU2FmDc
Thanks for the reply. The air filter I know is good, just checked that. I'll take a look at this video.
Ofcourse! I hope it works!