What was found
(CAN) WHILE ATTEMPTING THE FIRST START OF THE DAY THE ACFT SUDDENLY SHIFTED TAIL LOW AND TO THE RIGHT. IT WAS DETERMINED THAT THE RT REAR LANDING GEAR DAMPER HAD COLLAPSED TO THE FULLY RETRACTED POSITION AND OIL WAS LEAKING FROM THE PISTON CAP AREA. THE DAMPER WAS REMOVED AND SENT TO A REPAIR FACILITY. INSPECTION AFTER REMOVAL FOUND THAT THE CAP THREADED TO THE TOP OF THE PISTON ROD HAD BACKED OFF SUFFICIENTLY TO RELEASE STORED NITROGEN PRESSURE.