What was found
NR 2 ENGINE LOW OIL PRESSURE WARNING ILLUMINATED WHILE CRUISING AT FL330. INDICATED OIL PRESSURE WAS 15 PSI. A PRECAUTIONARY SHUTDOWN WAS PERFORMED. THE FLIGHT DIVERTED TO ATL AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND THE THREADS FOR THE MAIN OIL FILTER ATTACH STUDS PULLED OUT OF THE GEARBOX. THE GEARBOX WAS REPLACED. THE ENGINE WAS RUN-UP AND CHECKED OK. THE AIRCRAFT WAS RETURNED TO SERVICE.