Has anyone experienced oil varnish issues in their ACC fan drive gearboxes? A few of our plants with wet cooling towers have OE with premature gearbox failures due to overheating and varnish. Damage observed included bearing failures and excessive gear wear/spalling. Also would like to know what type of oil is specified in ACC gearboxes, and if anyone has switched their oil type to address any problems. The fix applied to our cooling tower gearbox failures involved replacement with larger gearboxes, switched oil type from polyalphaolefin (PAO) to polyalkylene glycol (PAG), and installed filtration units.