AT 35 MPH IN CITY TRAFFIC, THE VEHICLE SLOWED DOWN AND THE TACH ROSE AS IF I WERE IN NEUTRAL, I LET OFF ACCELERATOR AND VEHICLE JUMPED FORWARD AS IF IT WENT BACK INTO GEAR. AS VEHICLE STARTED GAINING SPEED I STEPPED ON ACCELERATOR AND IT SEEMED TO GO INTO NEUTRAL AGAIN AND THE TACH ONCE AGAIN ROSE. I PULLED OVER TO CURB IN CITY AND TURNED ON MY EMERGENCY FLASHERS AND EXITED VEHICLE. I NOTICED SMOKE COMING OUT FROM UNDER VEHICLE AND REACHED BACK IN AND TURNED VEHICLE OFF. I OPENED HOOD AND FLAMES CAME UP FROM THE CENTER OF VEHICLE BEHIND ENGINE, I WENT TO REAR OF VEHICLE AND GRABBED FIRE EXTINGUISHER AND TRIED TO PUT FIRE OUT BUT COULDN'T. NO WARNING LIGHTS OR GAUGES GAVE ADVANCE NOTICE THAT THERE WAS A PROBLEM. THERE WAS A TRAIL OF FLUID THAT STARTED AT LEAST 300' DOWN THE MIDDLE OF MY LANE BEHIND MY VEHICLE AND ENDED UNDER MY TRANSMISSION. THE ONLY PHOTO IS A VIDEO I POSTED ON FACEBOOK, I TOOK THE VIDEO WHILE WAITING FOR FIRETRUCKS AND POLICE.