This is how I come to my conclusion to not exceeding GVWR.
Here is what it says in the owner manual and tow guides.
“Note:
Trailer tongue (trailer king pin for 5th-wheel towing) load weight should be 10% (15% for 5th-wheel towing) of total loaded trailer weight. Make sure vehicle payload (reduce by option weight) will accommodate trailer tongue (trailer king pin for 5th-wheel towing) load weight and weight of passengers and cargo added to towing vehicle. Addition of trailer tongue (trailer king pin for 5th-wheel towing) load weight and weight of passengers and cargo must not cause vehicle weights to exceed rear GAWR or GVWR. These ratings can be found on the vehicle Federal Safety Compliance Certification Label.”
—OR—
Just take the word or a few very active posters that the factory information is incorrect and you can ignore manufactures GVWR but you should honor the manufactures ratings for the Axles (GAWR) which both are listed on the Federal Safety Compliance Certification.
Link
https://www.ford.com/cmslibs/content/dam/brand_ford/en_us/brand/resources/general/pdf/guides/18RV&TT_Ford_SuperDtyPU_Nov27.pdf
Next I contacted GMC Commercial Sales and ask about exceeding GVWR and loaded to GAWR and they sent me this link and this is the GMC official position.
http://www.gmc.com/gmc-life/how-to/understanding-gross-vehicle-weight-rating
I believe that it is very slim chance that you going to get ticketed for being over your trucks GVWR of even the GAWR/GCWR/tire ratings. My research turned to the legal side started at the link below.
“Towing in excess of the vehicle manufactures’s weight limits could not only prove dangerous but could be considered negligent In the event of an accident with an overweight personal vehicle, you could be held responsible for higher awards in a lawsuit for damages to other people, vehicles or property.”
Link: http://www.personalinjuryclaimsblawg.com/personal-vehicle-towing-liability-for-rvers/
Still not total convinced I made an appointment with my trusted family lawyer and he explained how manufactures specs on all kinds of products are used in civil court to gain higher awards and there doesn’t have to be a law prohibiting exceeding manufacture specs to play a role in court. The towing guids and the Trucks User manual will be gospile in civil court. The other question you might want to ask is what happens if a lawsuit exceeds my limits on my insurance policy and how to protect yourself. That question can’t be answered unless someone knows what assets would be exposed and what’s your income level. That was an eye opening meeting.
Also check with the local State Patrol, DOT scales operator, and a CDL Training center they agreed you should never exceed you GVWR and load to GAWR.
This is where my research led me and now I’m going to called the weight police and attacked. Your research may lead you in a different conclusion. Everything in life has risk but you have decided if the rewards are worth the risk. In my case towing above GVWR was not worth the risk.
What seemed strange to me that GVWR, GAWR GCWR, tire ratings are all manufacture ratings why would ignore just one but GAWR is not to be exceeded.
I love it when people say that the little lady behind the counter at the county offices can increase the payload of 1/2 ton truck to over 14,000 pounds that were set by engineers at the manufacturer sets. I guess those little ladies now have engineering degrees to work there. LOL