Year 2000 2500 series idles at 600 rpm but when driving the rpm stays at 1300 when you take your foot off accelerator...Only drops to 600 rpm when you begin to brake...Also, when your foot is off the accelerator and you're coasting at 1300 rpm if you shift to neutral it will immediately drop to 600 rpm... Any ideas?

 

Boy, that sounds like that issue is coming from between the steering wheel and the drivers seat.

 

That's uhh... what it's supposed to do. My 98 2500 does it too. I haven't had a truck of this style in a long time so I can't remember, but it may just be the way that the heavy duty 2500 transmission is set up

 

That is Normal.......as 92silvey said its the way the tranny is built and designed.