mechanic58, In my experience that will result in bearings that are overly tight.
Here is a manual for the next model years of trucks, I expect your axle is covered, still used in the newer truck. (click "contents" at the bottom for the whole manual)
http://chevy.oldcarmanualproject.com/gmc/5559mm/5559mm663.htmlLook here for other useful manuals.
http://chevy.oldcarmanualproject.com/Read the manual, but it explains basically hand tight while turning and back off 1/8 of a turn. More detail in the manual..
Grigg