All the reduction gearbox does is reduces the revs needed on the engine therefore lenghtening the life of the engine.Mine hasnt got one on and is still running like new after 3 years.Regular oil changes and maintenance are essential just like any other engine.
Your main concern is running the pump without water going through it,this will shorten the pumps life and therefore is essential to ensure that you have good water supply and thats where the buffer tank comes and not running direct from a tap.