What was found
DURING CRUISE ENG CONTROL FAULT R CASS MESSAGE ILLUMINATED. RAN QRH AND MESSAGE CLEARED. WHEN STARTING DESCENT FELT A VIBRATION THAT CHANGED WITH POWER SETTING CHANGES. OBSERVED THAT THE RIGHT ENGINE POWER CHANGES LAGGED BEHIND THE LT ENGINE BY 2-5%. REMOVED RH STARTER- GENERATOR AND INSTALLED OVERHAULED UNIT. FOLLOW ON CHECKS COMPLETE WITH NO DEFECTS NOTED. ENGINES RAN WITH EVEN N1% VALUES. ALL WORK IS DONE IAW AMM 80-10-20. THIRD PARTY VENDOR COMPLIED WITH TRANSIENT VIBRATION SURVEY ON BOTH RT AND LT ENGINE. THIRD PARTY VENDOR COMPLIED WITH LT ENG FAN BLADE CLEAN AND LUBRICATION. COMPLIED WITH ENGINE RUNS WITH NO DEFECTS NOTED AT THIS TIME.