Oh my god, this thread is terrifying.
Every piece of equipment that is used to tow something, between the engine, tow vehicle frame, vehicle axles, hitch receiver, hitch tongue, tow ball, trailer hitch, trailer frame, trailer axles, and trailer tires all have their own tow rating. When you're towing your tow limit is only as high as the weakest link in that chain. The ultimate cap is the
GCWR for the loaded tow vehicle and trailer. Even if you have upgraded your breaks and springs and other components, if you get into an accident and you are found to be over the OEM weight limit good luck getting your insurance to cover any of the damage or injuries you cause.
For me in my current setup, when the Yukon is fully loaded with gear, people, fuel, and the trailer tongue weight I am only 200# from exceeding the 4000# rear axle capacity. The next weakest link in my chain is the 5,000# trailer weight / 750# tongue weight distributing bars I use with my hitch. After that it is the 6000# rating of the 2" tow ball in the hitch, and so on after that.
@HiHoeSilver - I'll try and take a look for the slip when I get home.