NORMAL HIGHWAY SPEED I NOTICED A LOT OF SMOKE COMING FROM REAR OF VEHICLE I STOPPED AND HEARD A HISSING NOISE UNDER VEHICLE AND SAW OIL SPRAYING ON THE EXHAUST PIPES NEAR TRANSMISSION IT THEN CAUGHT FIRE PUT FIRE OUT I CHECKED FLUID LEVEL IN TRANSMISSION IT WAS LOW HELP SHOWED UP WITH OIL FILLED IT BACK UP CONTINUED HOME AT SLOW SPEED APPROXIMATELY 50 MILES LATER O.D. STARTED TO SLIP THEN DRIVE STARTED TO SLIP SO I DROVE 30 MPH IN 2ND WAS TOLD THAT TRANSMISSION WAS GOING OUT BECAUSE OF FLUID LOSS OUT OF VENT TUBE