WHILE IN REVERSE AND GOING DOWN A SLOPED DRIVEWAY IN WINTER CONDITION, VEHICLE SUDDENLY ACCELERATED TO AN UNKNOWN SPEED. IT CRASHED INTO A TREE ON OTHER SIDE OF THE ROAD. DEALERSHIP HAS NOT EXAMINED VEHICLE. *AK THE TRUCK WAS EXAMINED BY DEALER'S SERVICE DEPARTMENT. TECHNICIAN CLEANED LINKAGE AND MADE ACCELERATOR PEDAL EASIER TO OPERATE. THE TECHNICIAN STATED THAT A CARBON BUILD UP ON SOME RELATED PART WHEN ENGINE WAS COLD, MIGHT HAVE CAUSED A MALFUNCTION. *YH