Upvote:1
It CAN be possible, but when it comes down to it, it's going to be up to you to decide whether or not to take the risk.
I've flown from Christchurch to Sydney twice in the past three weeks (wedding season). Both times I went from on the tarmac in the plane, to on the train going into the city in under 20 minutes (last time was closer to 10 minutes!). Now it helped that I only had carry-on, but there are things I do that do help speed up. You can do some of them, and you can also prepare for the departure.
ARRIVAL
Have a look at the Sydney airport maps. Familiarise yourself with the airport terminal layout. Arrivals is on the floor under departures.
On the plane, have a pen ready, and fill out the arrivals card. Have all your documents ready. When the plane opens, RUN. I'm not kidding. I don't run, but I do make the effort to pass almost all the other passengers, because the lines at immigration and customs can be LONG (not as bad as I've had in Melbourne, but pretty frustrating).
If you can use the smart-gates, grab the first free terminal you see, process yourself, and head straight to the gates, and down to the baggage.
Now you're in the time where you don't have control - the bags might get delayed. Position yourself next to where the bags come out. Grab yours and head to the closest and shortest customs queue.
You'll have cleaned your tent and camping gear before the flight, right? DO SO. Also make sure not to have any of the other banned foods or plant material. Hopefully this will speed up your customs time.
Right, now you're out of customs. Turn right, and right again and you'll see the escalator up to Departures. Up you run, and...
DEPARTURES
you'll have checked in online if possible for your ticket, right?
Ideally you'll also have looked at the website before your flight from Christchurch and worked out which counter to head to. Head there and drop off your bag, hopefully in time.
Continue through the check-in area and you're max 3 minutes walk from customs. If you get through there, then you're probably home free and on your flight. Hooray, celebrate with a drink.
Alternatives
Ring up the airline. Perhaps they can offer an alternative flight. Virgin Australia, for example, will sometimes let you go on an earlier flight if there are seats available, even if you're on a non-changeable ticket (speaking from experience).
Failing that, you're going to have to decide on the risk of possibly having to buy another international ticket from Sydney, or buying a new one TO Sydney.
Good luck!