Is there a difference between the physical dimensions of the different classes of hitches? What I mean is that I once heard that the length from the end of the receiver tube to the hole for the hitch pin was different to not allow a larger hitch size to be put in to small of a receiver for safety. Im guessing the most common size of receiver is a 2 inch. So is there a size difference between say a class 2, 3 and 4 2" receiver or are they interchangeable?

 

Lets see, Class I and II are 1.25" ball mount with a ball shank hole of 3/4".

Class III and Class IV (usually Class III with an IV endorcement) are 2" recievers. Some 2" ball mounts have 1 and 1.25" ball shank holes.

There is only 1 Class V, 2" and it is a solid ball mount. All of the others are 2.5" all of which will have a 1.25" ball shank hole.

The depth of the hitch pin and hole diameter differers with hitch manufacturer's and has no classification bearing. The 2 main sizes are 5/8" and 1/2" diameter. Some manufacturer's reciver hitchs with be drilled for both hitch pin sizes.


Does all this makes sense?

EDIT:
Ball mount manufacturer's as well as reciever hitch manufacture's clearly label all of their hitch stuff with weight ratings to eliminate any possibility of using an incorrect weight range equipment for a specific load... or at least to limit any liability from those that fail to read it.

 

Ok so I can assume that not everything that fits into a 2" receiver hitch will necessarily fit EVERY 2" hitch. And do you think I can also say that everything that fits into a class 3 hitch will also fit a class 4 hitch?

 

Any 2" reciever should accept any 2" ball mount or accessory; whether it is a Class III or a Class IV. There are a very few 2" ball mounts with 1/2" hitch pin holes. These fit (hitch pin) too loosely in a Class III or a Class III with a Class IV endorcement with only a 5/8" hitch pin hole to be safe. If your reciever is drilled for both holes they are ok to use though.

The big problem is capacities.
Let's say you have a Class III with IV endorcement reciever hitch rated for 5000#'s or 10000#'s with weight distribution bars. These same recievers will have a 500# tongue weight capacity or 1000#'s with WD bars.
You could potentially buy a ball mount and ball rated for 6k, which correctly exceeds the reciever but then mount a trailer with a loaded weight of 14000#'s (1400#'s on tongue weight) not using WD bars and rip the reciever out of the truck frame.
I see this type of error on a regular basis as they blame a bad reciever hitch.

 

Ok thats the answer I was looking for. Thanks alot Colorado.