In the OP's post, he has a 17 foot trailer with tandem 3500 axles. That is two sets of axles. 3500 x 2 is 7000. That is enough to load a 3/4 ton pickup onto the trailer. when loading a pickup or a car even a small tractor the combined weight is with the capacity of the trailer and the weight is not isolated to one area.
When loaded the weight is spread out.
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