I have the rocket 3 touring 2012 and I've put 5000 mls on it, through all that riding the gearbox has sounded clunkey as you say , the hotter it gets the worse it goes.on a long ride my right and goes numb with the vibrations, but I have been stuck in traffic on the hottest days, been out riding in group's been camping on it ,been out for a blast on Britain's finest country roads and I have loved every minute. All bikes have their quirks and the rocket is no different, what you have to remember is 2.3cc kicks out some grunt so you need a lot of metal to keep it all in place, enjoy