Of course you know that the ton rating is achieved by adjusting the overload bypass. The pump used by the 2 ton, 3 ton and 4 ton Harbor Freight is the same, these are just adjusted differently. In the case of the Harbor Freight 2 ton which has the very long arm, (much longer than the Arcan 3.5 XL), the same as the Arcan XL2T, the rating is lower because the length of said arm. In general, the longer the arm, which serves as a lever working against the pump, the lower the rating, even using the same pump.
Another example of adjusting the rating with the overload is the case of the Hein Werner 93642, 2 ton and the Hein Werner 93652, 3 ton.
It just happens that both use the same of u-cup, part number wise, of the same size, which is 7/8 x 1 1/2 x 1/4 but the 93642 is adjusted at a lower ton rating than the 93652 as a marketing strategy, to try to have a bigger line of jacks. The 93652 has a slightly longer arm and still is rated higher because it is adjusted like that by the manufacturer to make it different from the 2 ton. This would be an exception to "the longer the arm the lower the rating" thing, but it is because the extra length of the arm in the 93652 is not too much compared to the 93642. But this mainly shows that the pump has enough capacity to allow an increase in the rating to 3 ton even with a longer arm.
One could increased the ton rating of the 93642 to 3 tons easily and maybe even to 3.5 tons if one had the machine necessary to measure the force applied by the pump. And the 93642 would make a better 3 ton than the 93652 because its arm is slightly shorter, therefore there would be a little less force acting against the pump.
The pump of the 93652 has a longer body, because it has a longer ram, but that does not account for the increase in rating. Everything else is the same.
So the Harbor Freight 3 ton could be adjusted to 3.5 tons without any problem.
