Our motor manufacturer states never to try to repair the motor or gearbox. Must be sent back for warranty work. (1 yr) They do not recommend opening up the gearbox, and they will not say what grease to use. BUT, since I want thing to last, I would use a high temp wheel bearing grease, but not too much. Since the motor does not set level on the feeder it is very important that the grease does not brake down and leak into the bushings of the output shaft. This would cause the coal fines to collect at the output shaft and ruin the bushing in no time. With the old style motors running full time (before Coal trol) the casing would get to hot to touch. The grease would run to one side of the housing but would still lube the gears as they were turning. Sometimes a little dab will do ya. More isn't always better, except with beer.