2002 FORD SUPER DUTY POWERSTROKE DIESELS WITH 4 WHEEL DRIVE. THE 4 WHEEL DRIVE SYSTEM ON THESE TRUCKS IS CALLED, "ELECTONIC SHIFT ON THE FLY" ... THERE IS A DASH MOUNTED KNOB ON THE DASH. THE NOB HAS WRITTEN, "4X2"-4X4 AND 4X4 LO". THIS PAST SNOW STORM IN NORTHERN NEVADA HAD CHAINS OR SNOW TIRE RESTRICTIONS. SO, ON MY WAY TO WORK I TURNED THE DASH KNOB FROM 4X2 TO "4X4. THE 4X4 SYSTEM LIGHT ON THE DASH LIT UP AND THE TRUCK WENT INTO 4 WHEEL DRIVE. SHORTLY AFTER DRIVING AND PROCEEDING FROM A "STOP SIGN" THE REAR TIRES STARTED TO SPIN, NOTHING FROM THE FRONT TIRES!! THE DASH LIGHT STILL SHOWED 4X4 MODE.. I PULLED TO THE SIDE OF THE ROAD AND TURNED THE KNOB FROM 4X4 TO 4X2 AND THEN BACK TO 4X4. AGAIN THE 4 WHEEL DRIVE SYSTEM WORKED.. UPON CLIMBING UP A SLIGHT HILL THE REAR TIRES STARTED SLIDING CAUSING THE BACK OF THE TRUCK TO "FISHTAIL". AGAIN, WITHOUT WARNING THE TRUCK LEFT IT'S 4 WHEEL DRIVE MODE AND WENT BACK INTO 2 WHEEL DRIVE..THIS IS EXTREMLY DANGEROUS!!!!THE TRUCK UNLIKE A 4X4 SYSTEM THAT JUST DOES NOT WORK OR QUITS WORKING, TELLS THE DRIVER IT IS IN 4X4, BUT WITHOUT WARNING, GOES BACK INTO 4X2 MODE. THIS DEFECT CAN CAUSE PROPERTY DAMAGE, AN ACCIDENT OR EVEN DEATH!!! PLEASE LOOK INTO THIS MATTER!!! ALL OWNERS OF THIS SETUP, WHICH INVOLVES MODEL YEARS 1999, TO 2004 SHOULD BE ADVISED BY FORD AND TO REPAIR PERMANTLY THE FLAW..IF YOU NEED FURTHER INFORMATION, PLEASE CHECK WWW.THE DIESEL STOP.COM.. THIS IS AN INTERNET WEB SITE DEDICATED TO THE OWNERS OF FORD DIESEL PICKUP TRU