A SAAB 340 IN CRUISE AT 17000 FT DECLARED AN EMER AND DIVERTED DUE TO THE L DC GENERATOR FAILURE AND L ENG VIBRATIONS.

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WHILE CRUISING AT 17000 FT ON ACR AIRLINES FLT XYZ FROM EVANSVILLE; IN; TO DETROIT; MI; WE EXPERIENCED A GENERATOR OVERTEMP ANNUNCIATOR ON THE L GENERATOR AND PERFORMED THE EMER CHKLIST. AS INSTRUCTED; WE SHUT DOWN THE L GENERATOR BY OPENING THE RELAY. THE L GENERATOR LIGHT ILLUMINATED; CONFIRMING THIS. THE L GENERATOR OVERTEMP LIGHT EXTINGUISHED AFTER APPROX 2 MINS. OVERHEAT CONDITION RESOLVED. MAINT WAS NOTIFIED. THE FLT WAS IN VMC AND AGREED WITH COMPANY TO CONTINUE TO DTW. AFTER ABOUT 10 MINS; THE L OVERTEMP LIGHT REILLUMINATED. DISPATCH WAS NOTIFIED ALONG WITH MAINT THE FLT WAS NOW DIVERTING TO INDIANAPOLIS. IN OUR JUDGEMENT IT WAS THE SAFEST DECISION BECAUSE THERE WAS NO MORE PROC TO FOLLOW AND WE WANTED A MECH TO LOOK AT THE GENERATOR. WE NOTIFIED ZAU AND DECLARED AN EMER AS OUR L ENG BEGAN TO VIBRATE WITH VARIATIONS IN TORQUE. ONCE THE PWR WAS REDUCED FOR DSCNT; WE DECIDED TO KEEP THE ENG RUNNING AS ALL OTHER INDICATIONS (OIL PROP AND ENG; TORQUE; ITT; NG) WERE RELATIVELY STABLE AND ENG WAS PRODUCING PWR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE PROB WAS A MECHANICALLY FAILED GENERATOR BUT WAS NOT ADVISED IF THE GENERATOR ACTUALLY CAME APART. THE RPTR SAID THE GENERATOR COOLING OVERBOARD VENT WAS ALL SOOTED UP AND WAS A GOOD INDICATION THAT THE GENERATOR WAS INTERNALLY DISINTEGRATING.