EF100-400/4.5-5.6 L IS Zoom does not slide easily

[Samwicensis]

 

Having some trouble with my zoom lens grinding and scraping on the shaft. When changing tension ring all the way to smooth there is still so much resistance it scrapes. See pic attached

[ebiggs1]

You have some grot in the mech. It needs to be cleaned but Canon doesn't service that lens any longer so a private repair shop might be able to do it.