What is range of RPMs (from-to) I should see at idle on '02 HD with a/c off by watching tach that is part of cluster instrument test?

Thanks in advance!

ZoranC

 

To be more specific:

Last night when in park is was moving irregularly from 680 to 780. I didn't check what it was doing when in drive.

This morning I did two sets of checks: First when truck was cold and was not started since last night. Second after I have driven truck for approximately few miles.

When it was cold and in park it started at average of slightly less than 1300 RPM, then it slowly settled down to 900 RPM and it stayed that way. After it was averaging 900RPM in idle for a while I moved it to drive and after it settled it was averaging 780 RPM in drive.

Then I took it for a drive for few miles (surface streets, 25-45mph), parked for 15 minutes, and took it back. On return I did not see surge in RPMs when turning it on, idle when parked was averaging 780RPM, and idle when in drive was averaging 630RPM

All checks were conducted with everything off.

Is this normal range and behavior?

ZoranC

 

Probably different cuz i don't have a s/c but my truck idles at 800 rpm steadily at rest