I have this version of the lens, and it's my best glass I'm sure.
Check the push-pull part of the barrel: if the --M-- is showing by itself you are disengaged from the AF pin. Push the barrel forward so that --AF-- shows above the --M-- and you're engaged in AF mode. For least wear and tear on the lens you must put the barrel in manual focus mode
and switch the camera body to MF for manual use.
2nd try
When mine is off the camera and in AF mode, the ring turns easily but focus is unaffected. If that is what you meant, then yes that is normal! Sorry if I took your message in another direction.