ON 01-24-2019, I STOPPED AT A RED LIGHT AND NOTICED AN ODOR COMING FROM MY 2017 FORD F-150 TRUCK AND SAW SOME SMOKE COMING FROM UNDER THE HOOD. A MOTORIST NEXT TO ME POINTED TO THE BOTTOM OF THE TRUCK; I ROLLED DOWN THE WINDOW AND HE SAID HE THOUGHT THERE WAS A FIRE UNDER THE TRUCK. I PULLED OVER, SHUT OFF THE TRUCK, SAW A SMALL FIRE ON THE FRAME UNDER THE ENGINE. THE OTHER MOTORIST PUT IT OUT WITH A FIRE EXTINGUISHER. A STATE POLICE OFFICER CALLED THE FIRE DEPT. WHO FURTHER EXTINGUISHED THE SMOLDERING. THE VEHICLE WAS TOWED. MY INSURANCE COMPANY SENT AN ADJUSTER WHO CONCLUDED THAT THE FIRE WAS CAUSED BY A FAILED PINON SEAL IN THE DIFFERENTIAL, WHICH IS PART OF THE POWER TRAIN. THE LEGAL DEPARTMENT OF FORD MOTOR CO. (OFFICE OF GENERAL COUNSEL) STATED THAT THE FIRE OCCURRED BECAUSE THE VEHICLE WAS DRIVEN ON PAVEMENT IN 4WD. I ASSERT THAT THIS IS NOT TRUE AND IS A TACTIC OF FORD MOTOR CO. TO AVOID HONORING THEIR PRODUCT WARRANTY OR TAKING RESPONSIBILITY FOR A POTENTIAL SAFETY HAZARD.