Hi tinytrooper the 6n7 means the truck came with the big tire package and the 9jv means of course the 10.50.15 tires which should have came on this truck with the sno flake wheels, so it looks like you got the 4.77, the pickups never came with the 4.77 , if they had the big tire package they would have came with 4.56 instead of 4.30,,only in 4wd , the 2wd came with 4.11 either automatic or 5 spd 2.6 only , the few 3.1 v6 pickups that came with the big tire package came with 4.56 also Jerry