GVWR is the maximum weight that a vehicle can weigh per the manufacturer. It is based on the assembled components including the weakest link. GAWR is the weight rating for one single component the axle. Loading to GAWR would likely overload the weakest link in the chain. Usually tires, but could also include things like springs, drive shaft, frame, wheels heck even safety equipment like seat belts. There is a retired GM engineer on the forums whos job was as a certification engineer. His basic job was to submit certification requests to the Feds for vehicles. He is very knowledgable in the process and what it all entails.