Also, the Diesel payload is 1900 and the Hemi is 2900.
With MegaCab, 5 people, and luggage, it seems like the tongue weight of a large trailer plus us will go over 1900 pounds, yet it looks like most 2500's are sold with Diesel.
What am I not understanding?
Because those who know, know that those numbers are farce and are due to government regulations rather than what the truck can handle.
The US DOT(Department of Transportation) and EPA(Environmental Protection Agency) classifies on-highway vehicles in 8 different classes with class 2 being broken down into two different segments. The classes for the light duty(yes a 350/3500 is considered light duty) are as follows;
Light Duty
Class 1: 0 - 6,000 lbs GVWR (small cars and midsize trucks)
Class 2A: 6,0001 - 8,500 lbs GVWR (150/1500 trucks and vans)
Class 2B: 8,501 - 10,000 lbs GVWR (250/2500 trucks and vans)
Class 3: 10,001 - 14,000 lbs GVWR (350/3500 trucks and vans)
The GVWRs for the rest of the classes can be found
here.
In most cases, how a vehicle manufacturer determines a vehicles GVWR is by looking at all of the specs of the truck like the frame strength, braking ability, and GAWR to come up with a number that the vehicle can handle. To get the payload number, the vehicle manufacturer subtracts the curb weight of the vehicle from the GVWR. The closer the curb weight the truck is to its GVWR, the less payload it will have. Now here is where it gets complicated.
In the case of Class 2b trucks where 2500s diesels are, the truck reaches the max GVWR of the 2b class (10,000 lbs) long before the specs of its parts can handle. Take my 2014 Ram 2500 CTD for example. My truck is limited by the class it is in rather than the sum of its parts. How can I say this? Easy, take a look at the parts and their ratings in other vehicles.
My 10,000 lbs GVWR Ram 2500 with a little over 2,100 payload shares the same engine, transmission, front axle, front suspension, rear axle, tires, axle gearing, driveline, brakes, and frame as the SRW 3500 CTD 11,700 lbs GVWR that has a payload of over 3,900 lbs. How is it that my truck has the same front GAWR of 6,000 lbs as the 3500 and a rear GAWR of 6,500 lbs (which is only 500 lbs less than the 7,000 lb rear GAWR of the 3500) yet my truck has almost 2,000 lbs less payload then that very same 3500 SRW. Remember, they are identical trucks except for the rear suspension which is only rated to handle 500 lbs less by its GAWR. If you take away 500 lbs from the 3500s 11,700 lb GVWR, then that would leave you with a 11,200 lbs GVWR which would give me a payload of well over 3,000 lbs.
Lets see what that rear suspension can handle in other trucks. In the identical truck like mine, but with an almost 1,000 lbs lighter 6.4L, the truck has a 10,000 lbs GVWR with over 3,100 payload. Hmmm, seems odd. I have the same rear coils as this 6.4L in my CTD, yet it is only rated the exact weight difference of the engine. Now, before you say "the extra weight of the engine is what does it". Remember that the rest of the truck is the same as the 3500 which is rated to handle much more weight and the engine rests on the front axle system which should not affect the rear suspension at all.
So why does it have less payload even though the very same coils in the rear can handle more in another truck? Because my truck reaches the max GVWR of it's class long before it reaches the capabilities of its parts. If my truck had the same payload as the 6.4L version of mine, then it would have a GVWR of over 10,000 lbs which is a class 3 truck and is where the 3500 truck resides. Ram has to comply by this class rating and so does every other manufacturer. So you end up with a 2500 with a maxed out GVWR of 10,000 lbs (going by regulations) which in turn makes the payload low because payload is derived from subtracting the curb weight from the GVWR.
If you actually went by the specs and ratings of the 2500 parts then you will see it can handle way more than the low payload it is given to comply with the 10,000 lb max GVWR of its class and it's real GVWR should be around 11,200 which would increase its payload to about 3,300 lbs. In many states this does not even matter at all because they do not have laws requiring a payload sticker unless it is being used for commercial purposes. What really matters is what you register your truck as. There are even some states that actually allow you to register your vehicle as a higher GVWR vehicle just as long as you are willing to pay the higher fee for it.
Also keep in mind that this does not apply to Ram 1500s. All Ram 1500s have a GVWR less than 7,000 lbs which you can see in the chart above is considerably less than the max 8,500 lbs of their class. This would mean that something else is limiting the 1500s, and it is not limited by its max class rating like the 2500s are.
I know it was long, but I hope it helped you better understand.
