2001 2500 HD with 8.1.
fan is either knocking or hitting shroud on cold morning startups, until engine warms up.
I’ve only had the truck for 3 months so it never happened until morning temperatures dropped to around 50 F.
anyone experienced this?

 

Well, it the fan is hitting the shroud, you should be able to see where it is hitting. If there are no areas of scraping, then I would say you need a new fan clutch. Be sure and purchase a decent one and not a no-name, bottom of the barrel chinesium unit that is priced so low it is unbelievable. Decent ones are ACDelco/GM Genuine, Hayden/Four Seasons, Behr/Mahle.

Good Luck!