My Honda Jazz, now out of warranty, has been experiencing similar gearbox troubles as reported by some of your readers. Three years ago vibrations started to occur when moving off uphill. The dealer's solution was to flush the gearbox and put in new oil and the "fix" would last for approximately 10 months before the procedure had to be repeated. Honda wants me to pay $220 every time this happens, something that should have been taken care of under warranty. What should I do now, tackle the dealer, go to Honda Australia, or go to Consumer Affairs?
Hopefully you have kept a record of the times the oil has been changed and the result. I would take that to the dealer in the first instance and present a claim to have the gearbox replaced, as has happened with some other Jazz owners. If that doesn't get the result you want, move up the chain, and if necessary go to the consumer affairs people as the last resort.