WITH MY FOOT ON THE BRAKE, I PUT THE TRUCK IN REVERSE TO BEGIN BACKING OUT OF A DRIVEWAY. I APPLIED A LITTLE GAS TO SLOWLY BACKUP AROUND THE TURN IN THE DRIVE. AS I WAS ROLLING BACKWARDS, I HAD MY FOOT ON THE BRAKE BECAUSE I WAS NAVIGATING PAST OTHER PARKED VEHICLES. AS I WAS CLEARING ONE OF THE VEHICLES, THE TRUCK SUDDENLY JOLTED BACKWARDS HITTING A TREE. SO THEN, WITH MY FOOT ON THE BRAKE, I PUT THE TRUCK IN DRIVE SO THAT I COULD PULL FORWARD AWAY FROM THE TREE. AS I BEGAN TO PRESS ON THE GAS PEDAL AND THE TRUCK INSTANTLY THRUST FORWARD, HITTING ANOTHER TREE, STOPPING THE TRUCK & KNOCKING THE TREE OVER. IT HAPPENED WITH SUCH POWER THAT THE WHEELS SPUN DOWN INTO THE MULCH BED BEFORE I WAS ABLE TO BRAKE, PUT THE TRUCK INTO PARK AND REMOVE THE KEYS TO TURN IT OFF. WHILE THE DAMAGE ON THE BACK BUMPER WAS MINIMAL, THE DAMAGE TO THE FRONT OF THE TRUCK WAS EXTENSIVE & THE INSURANCE COMPANY DECLARED THE TRUCK A TOTAL LOSS. THERE WAS ONE OTHER TIME, WHILE ON THE LOCAL HIGHWAY AT A STOPLIGHT, WITH MY FOOT ON THE BRAKE, THAT THE TRUCK BEGAN TO THRUST FORWARD ON ITS' OWN. AFTER IT FIRST ROCKED FORWARD, I PRESSED THE BRAKE ALL THE WAY TO THE FLOOR WHICH PREVENTED IT FROM ACTUALLY MOVING FORWARD ANY MORE. ONCE THE LIGHT TURNED GREEN, THE TRUCK SEEMED TO RETURN TO NORMAL FUNCTIONING. THIS INCIDENT OCCURRED AROUND THE TIME I WAS DUE FOR A TUNE-UP SO I FIGURED IT WAS A FLUKE AND WOULD HAVE BEEN RESOLVED WITH THE TUNE UP.