What was found
APPROXIMATELY 2 20 INTO THE FLIGHT WE FELT THE AIRPLANE SHUDDER AND SAW EICAS MESSAGES: L & R UTILITY BUS. RAN QRH AND COMPLIED WITH CHECKLIST. AFTER SEVERAL MINUTES WE NOTICED THE APU HAD SHUT DOWN. DUE TO LOWER WEATHER IN BNA CONTINUED TO MEM. EMERGENCY DECLARED. THE AMTS REMOVED AND REPLACED THE APU ECB FOR THE APU AUTO SHUTDOWN. OPS CHECKS GOOD IN ALL PHASES OF RUN. REMOVED AND REPLACED L/H ENGINE IDG. OPS CHECK AND LEAK CHECK GOOD AIRCRAFT GOOD FOR SERVICE