I did not write clearly. It is not the weight of the truck + the weight of the trailer. It is the GVWR ( truck weight + rated load weight) + Weight of trailer + load rating of the trailer = GCWR. A truck with GWVR of 7,000 lbs will be over the weight with a trailer that has a load rating of 3,000 lbs. Because the GCWR has to include the actual weight of the trailer along with the weight carrying capacity of the trailer.