Look at the hitch it should say it. Towing capacity is not what the truck is capable of pulling power wise. Its what the frame and hitch can handle. A class III hitch is good to 6000 lbs, a class IV is good to 10 or 12k lbs and class V is good to 16k lbs. I'm not a hundred percent on the numbers, thats just off the top of my head. I'm pretty sure the class III is 6k lbs though. But the info should be on the hitch
NO NO NO NO NO NO NO NO NO NO NO NO!
On all vehicles not only the Expy's you actually do need to find out what the truck was equiped with in order to find out what your total payload can be. The Expy's ran a few different gear ratio's in them along with the upgraded tranny cooler and so forth if equiped with a factory tow package. For the 2002 model the max load rating is listed on page 181 of the owners manual. It breaks it down by 2wd or 4wd, Engine size, Axel ratio, and Tire rim size, if you do not fallow these guide lines you could severly overload your vehicle and cause an unsafe driving condition ( OR WORSE AN ACCIDENT ). You also need to factor in the weight rating of your tires so that you do not overload them as well.
Engine Gear Rim Maximum Trailer weight
Size Ratio Size GCWR range
( ALL WEIGHT RATINGS ARE IN LBS )
4.6L 3.31 (16) (11 000) (0-5 900)
4.6L 3.31 (17) (11 000) (0-5 900)
5.4L 3.31 (16) (12 000) (0-6 800)
5.4L 3.55 (16) (13 000) (0-7 800)
5.4L 3.55 (17) (13 000) (0-7 800)
5.4L 3.73 (16) (13 500) (0-8 300)
5.4L 3.73 (17) (13 500) (0-8 300)
4x4
4.6L 3.55 (16) (11 500) (0-6 000)
4.6L 3.55 (17) (11 000) (0-5 500)
5.4L 3.31 (16) (12 000) (0-6 400)
5.4L 3.55 (16) (13 000) (0-7 400)
5.4L 3.55 (17) (12 500) (0-6 900)
So IT DOES NOT ONLY DEPEND ON THE HITCH THAT YOUR VEHICLE HAS but that is a factor along with all the others listed above. Anyone could mount a class V hitch under a vehicle even if the frame is not rated to carry that kind of load, not only the frame but the suspension and the rear axle itself (especially since these are 1/2 ton platforms and NOT 3/4 ton).
Mine is a 2wd 5.4L with the 3.55 gear ratio and 17in rims. So I have a max trailer weight raiting of 7,800LBS as long as my GCWR (Gross Combined Weight Rating ) does not exceed 13,000LBS (fully loaded with all passangers and cargo + trailer). My Expy is also equiped with a Class IV hitch factory SO WHAT YOU ARE SAYING IS THAT I CAN PULL A TRAILER THAT WEIGHS BETWEEN 10K - 12K LBS ( BECAUSE THAT IS WHAT THE HITCH IS RATED AT ) WHEN IN REALITY MY VEHICLE IS ONLY RATED TO PULL A TRAILER THAT WEIGHS 7,800LBS. If you over load a vehicle like that you are asking for problems, sure with the power of the 5.4L I could probably PULL that kind of weight ( since the same motor is used in the Super Duty trucks ) but the vehicle itself will not hold up to that kind of weight. Just because the HITCH has a weight rating does not mean that the vehicle will have the same rating because 99.999999% of the time the Hitch can take more of a load than what the vehicle can!
Make sure you find out what your vehicle is rated to tow ( you can also find this info on the sticker inside the drivers door ) and DO NOT JUST GO BY THE HITCH RATING!!!!!