The out drive gear lube resevoir was removed form my engine during removal of the engine for a y tube exhaust repair. I would like to clean out the resevoir of any residual sludge and re-fill it. I remember reading somewhere that the outdrive gear lube system needs to filled from the lower unit back into the resevoir. I this true? Can I just put frseh gear lube back into the resevoir without any problems?