2wd & 4wd

without actually hearing this myself, it could be the gear moving slowly and engaging slowly into 2wd. Or your syncro or shift fork is wron out.

I run the truck in 2wd going roughly 60 mph then slow down to a stop thats when i hear the very loud abnoxious grinding noise. The noise will go right away as soon as i push the 4wd hi button. Why is this?

read the reply i sent if it is changing on it's own without you pushing the button to go to 4wd then eithere your t-casemodule is bad or you have a shorted wire that is causing it.