you said your truck weighed 18,900 and that does sound lgt. for a 106 with a 96 aa slpr [ is it a fyda trk or a mgf trk ] manual or auto. anyway , you have a 33,000 gross but legal in most states is the std. 12000 front and 21000 rear they really dont care what the door sticker says its the amt. the tires are load rated for in single or dual form but the std. 12/21 will keep you out of trouble no matter where you go as for the amt of payload you simply cant just take gross wgt and subtract the wgt of the trk and claim that is what you can hall hitting that 12/21 split perfect is real hard to do , do yourself a favor and give a 500 # cushion so you can move frgt up or back to get axle wgt rite. now back to the trk that is one of the litest 106s w/96 slpr i have heard of most of the fyda trks w/autos and tool boxes, 96" slpr, 80 gal tanks are in at 19800 to 21400 and the mgf trks made the same are only a little under that but weight usually isnt a problem , i cant see losing loads over it . i have a 112 bus class frtlnr w/96aa slpr and the big mercedes and all of the afore mentioned acc. trk weighs 22,460 thats 11760 front and 10700 on the rear and have only had a couple of loads i couldnt hall hope this helps but would like to hear more info on your truck and what all it has and had in it when you weighed it