Scooby
My Navistar the sun of axle capacity is manufactures gvwr. But with this said. Some items like the RA, the 12.2k limit was tires. Axle, springs etc is 16500. Put higher rated tires on it.....
Front axle itself is 6000. Empty 5900....springs 8k, tires initial 7200.
Gvwr per door tag in OM at house, 18200.
I've seen a number of trucks class 5/6 and above where axle totals equal gvwr. BUT the FBL loads take 25-30k RA ratings to 20k or 24k depending upon use on type of truck or trailer...
Marty