You should be paying tonnage now on your truck. Look to see what the green registration paper says under GVW. If it says 8000, that is ALL you are legal too. If 10000, again all you are legal too.
To change it, next time you pay for you yearly tag, ask to have a 10K plate registration if you have 8000. About $15 more than you pay in tonnage now. Same going from 10-12K. Going from 12-14K, you get hit with a $75 or so DOT tax. Wouls suggest you not do that unless you really need too!
The basic tonnage you have to pay for is tare/empty weight times 1.5, then go to the next higher ton. If you weigh 4700 like my reg cab C2500, I can register at 8000 lbs. My 96 crew cab was 6600, so it needed to be at 10K. IIRC I had it at 12K. Door sticker gvwr means squat here. Other than it being a performance warranty standard at dealership. Go over, they "COULD" deny you warranty coverage.
Been pulled over in my Navistar dumptruck at 150% of door sticker wt, no over weight ticket. I did get a up my gvw by 2000 lbs with in 10 days, as I was 800 or so lbs over my 26K paid for registration. If you were to get pulled over in the 10,xxx lbs relm, my suspicion is, the same would happen to you, get a 12K plate if you had a 10K plate. Maybe the same if you have an 8K plate. The WSP enforces the Federal Bridge Law road bed design limit standards. Which is max 20K per axel, with at least 40" of tire width, or 500 lbs per inch width of tire. This is the engineered point load spec of the road, that LEO/CVEO's have to enforce. Door sticker means squat!
Now if you were to run down the road at 20K lbs with current truck, about the max you could be with singles on a typical 25 series truck, or any pickup.....you would get taken off the road by a violation. It would not be weight driven per say. more like your brakes do not stop you within 25-30' from 25mph. That fine is WAY worst than an overweight ticket, along with it follows you on your driving record. Along with your truck gets red tagged and can not be driven to the nearest service facility. It gets flatbed hauled, or fixed at that site......not fun.
Look up RCW 45.xx.xx for weight laws of Washington state. RCW 46 will relate to the speeds you can go with a trailer or over 10K gvw. Max of 60 mph no matter where you are!
Reality is, going over the manufacture gvwr is legal.......remember, there are OTHER laws that might get you pulled off the road that hurt you worst!
Marty