Attention: TDR Forum Junkies 
Called the CHP Commercial Vehicle Section at (916) 843-3400 this morning and spoke to an officer about this topic. Also found the info online at http://www.dot.ca.gov
Some info copied from DOT regulations:
DO THESE VEHICLES HAVE TO STOP AT THE SCALES?
PICKUP -- It depends on the gross vehicle weight rating (GVWR), unladen weight, and bed of the truck.
GVWR under 11,500 pounds, unladen weight of less than 8,001 pounds, and open box-type bed not exceeding 9 feet in length -- NO.
GVWR 11,500 pounds or more, unladen weight 8,001 pounds or more, or not equipped with an open box-type bed not exceeding 9 feet in length -- YES.
Seems to me that the manufacturer rates the GVWR on a 3/4T pickup lower than GAWR to avoid the need to stop at the scales every time.
Something else the CHP officer told me is the following:
A driver must have a fifth-wheel recreational trailer endorsement added to his/her Class C driver license to pull a fifth-wheel recreational trailer over 10,000 lbs., but not over 15,000 lbs. GVWR, which is not used for hire. This endorsement is not required if the driver has a commercial or noncommercial Class A driver license.
Some info copied from DOT regulations:
DO THESE VEHICLES HAVE TO STOP AT THE SCALES?
PICKUP -- It depends on the gross vehicle weight rating (GVWR), unladen weight, and bed of the truck.
GVWR under 11,500 pounds, unladen weight of less than 8,001 pounds, and open box-type bed not exceeding 9 feet in length -- NO.
GVWR 11,500 pounds or more, unladen weight 8,001 pounds or more, or not equipped with an open box-type bed not exceeding 9 feet in length -- YES.
Seems to me that the manufacturer rates the GVWR on a 3/4T pickup lower than GAWR to avoid the need to stop at the scales every time.
Something else the CHP officer told me is the following:
A driver must have a fifth-wheel recreational trailer endorsement added to his/her Class C driver license to pull a fifth-wheel recreational trailer over 10,000 lbs., but not over 15,000 lbs. GVWR, which is not used for hire. This endorsement is not required if the driver has a commercial or noncommercial Class A driver license.
