what would make a 4.7 motor overheat in regular stop/go traffic within 15-20 min

Hello, my initial thought would be to look at the cooling fan. Start and stop traffic limits the amount of natural air flow coming through the grille and radiator. If the cooling fan does not operate. there is no way to get air blowing through the radiator to cool the coolant. I would also check to ensure there is no air pocket in the cooling system. You could also check for a shop near you to give you some insight! Good luck.

In addition - This particular engine does not react well at all to overheating .. Continued operation in this condition may result in serious cylinder head/piston damage from dislodged exhaust valve seat(s) .. (Just so you are aware.)