With 40,000 miles, mine knocks quite a bit for atleast a minute or two. It seems to be getting worse as time goes on. It used to only do it in the mornings but now it does it after just letting it sit for an hour or so. With all this noise, I should have just got the Duramax! (I'm wishing I would have done that anyway!!)[i]Anyone else have problems with the 6.0 knocking at start up ?? [/B]
I've heard some people that tried the top-end cleaner to reduce the knock but I don't think it helped much. There used to be a "GM Piston Slap" website but it doesn't seem to exist anymore. I know GM threatened the owner of the website on more than one occasion - not sure what ever happened.