THE OEM NUT HOLDING THE PINCH BOLT TO THE UPPER CONTROL ARM IN MY 2006 JEEP GRAND CHEROKEE LIMITED CAME LOOSE AND ULTIMATELY FELL OFF. THIS CAUSED THE UPPER CONTROL ARM TO SEPARATE FROM THE VEHICLE, WHICH RESULTED IN THE FRONT DRIVER'S SIDE WHEEL AND HUB ASSEMBLY BREAKING OFF FROM THE AXLE WHILE IN MOTION. THE VEHICLE CAME TO A STOP WITH THREE INTACT WHEELS AND THE DRIVER'S SIDE WHEEL UNDERNEATH THE BODY. FORTUNATELY, THE VEHICLE WAS NOT AT HIGHWAY SPEED OR SEVERE INJURY OR DEATH WOULD HAVE BEEN PROBABLE, DUE TO THE LOSS OF THE ENTIRE ASSEMBLY AND THE LOSS OF ALL BRAKE SYSTEM HYDRAULIC PRESSURE, AS THE BRAKE LINE WAS ALSO SEVERED. THE OEM NUT HOLDING THE PINCH WELD TO THE UPPER CONTROL ARM APPEARS INADEQUATELY DESIGNED TO WITHSTAND ROUTINE REMOVAL AND RETIGHTENING FOR SERVICE SUCH AS WHEEL ALIGNMENT AND SUSPENSION ADJUSTMENTS. THERE APPEARS TO BE INADEQUATE ENGINEERING THOUGHT INTO ENSURING, AT A MINIMUM, A SIMPLE MECHANISM TO SECURELY FASTEN THE NUT (E.G., COTTER PIN, SERRATED FLANGE, OR OTHER LOCKING FEATURE). THIS IS A SEVERE OVERSIGHT GIVEN THE POTENTIAL DANGER ASSOCIATED WITH AN UPPER CONTROL ARM SEPARATION AT SPEED. *TR