The tag in the door will say what the gross weight can be max. That's what the truck with driver and load will weigh max if sitting on a scale.
The payload is the weight in the door less the empty truck weight.
For example, my 52 3800 (1 ton) says 8,800 lb in the door, and weighs 4,400lb empty. I can put a load of 4,400 lb in the bed, and have.
If you want to get really picky there will be a max weight you can have allowed by the factory of each axle, and this adds up to the gross weight. So, the front axle is good for X,000 lb, and a different number for the rear, to load the truck to capacity you would need to think about weight distribution when loading.
Grigg
