Size matters.
Class 1 hitch has a steel plate, and a 3/4" hole for the ball mount, and the mount is not removable. It has a maximum rating around 2,000 or 4,000 pounds, depending on the design.
Class 2 is rated a little higher, and has a 1-1/4" square opening to prevent someone from inserting a 10,000 pound hitch ball into the tiny hitch (presumed to be on a tiny car) and towing something WAY over the weight class for that hitch. It is good for cars, light pickups, and SUV's. Maximum rating is typically 3,500 pounds.
Class 3 is typically 2" square and was rated at a minimum of 5,000 pounds GTW and 500 pounds deadweight when it first came out. There was not a specific 'maximum' weight rating for class 3, but later was defined as class 5 when they came out with much heavier rated hitches. Class 5 was not 'official' but like a slang term, became accepted over time.
So class 3 is anything above 5,000 pounds (though some might be rated at 3,500 like the one on my motorhome by the manufacture to limit people from towing to much with the wrong vehicle). It will have a 2" opening with 'round' corners that will not accept a weight distribution hitch. However if the hitch is rated at more weight, and is rated to accept a weight distribution hitch, then it will have a full 2" square opening, so it can accept a WD hitch ball mount.
When Ford started rating their trucks to tow 12,000 pounds, they started installing 2.5" hitch in the trucks. This was considered class 5.
Even before Ford rated their hitch for 12,000 pounds, Titan (and perhaps others) started building 'Heavy duty' hitches with 12,000 pound ratings and 2" openings for WD units. Later they started building 2.5" hitches (in the 80's and early 90's) with 10,000 + pound ratings. These where marketed as class 5.
You can buy a 16,000 pound rated truck hitch for dually pickups and the cab and chassis dually trucks. It will have dual receivers. Some have a 2.5" and 2" opening, so that you can use either to tow with, or a 2.5" hitch extension, or a 'super truss' hitch with both 2.5" and 2" hitch that can be 48" long and still rated to carry the load of a 5,000 pound trailer. These super truss hitch extensions are popular with the Rodeo crowd, who might have a Lance Camper with a 48" extension over the back bumper, as well as tow a 2 horse trailer with about 5,000 GTW!
So that is about all I know about trailer class ratings!
You can check this place for more information.
ETrailer.com That is where I would recommend getting a price quote for your hitch, if you have not bought one already. They sell the hitch receivers, and you can get those with a 5,000 pound rating and 1" hole for the ball mount, or 3,500 pound rating where the hole is 3/4" so that you can not install a 5,000 pound rated ball in the light duty receiver.
But with shipping, it probably is easier and more convenient to pick up the hitch locally. I discovered that my local U-haul wants something like $376 for a hitch for a 2001 E-350 while E-Trailer only wants $178. I did not check shipping, but they did offer a free shipping offer for orders over $99 last month, probably will offer that again, or if you ask nicely.
Have fun camping!
Fred
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Porsche or Country Coach!
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