The old designations of 1/2 ton, 3/4 ton, and 1 ton are not relevant any longer. The better way to compare is the GVWR rating of the vehicle. A Chevrolet 3500HD Crew Cab/Long Box SRW with the 6.0 engine and 4:10 gears has a payload capacity of 4,147#. Same truck with dual rear wheels can carry 6,111#, 1 ton more, yet they would both be called "1 ton" by the old terminology. I believe the manufacturers still use the old designations, for example GM uses 1500, 2500, and 3500, simply for marketing and to compare to other brands, Sierra 1500 = F150 = Ram 1500. Who knows some day we may use the DOT classification. The DOT Class 1-3 are classified as Light Duty.
GVWR
Class 1 0 - 6,000 lbs
Class 2 6,001 -10,000 lbs.
Class 3 10,001 - 14,000 lbs.
Class 4 14,001 - 16,000 lbs.
Class 5 16,001 - 19,500 lbs.
Class 6 19,501 - 26,000 lbs.
Class 7 26,001 - 33,000 lbs.
Class 8 33,001 lbs.+