You can get day permits from RTA which allow you to drive from one destination to another only. But it aint worth you driving down from sydney to melbourne.
Reasons;
1. You will definetly add a few scratches to your car. Not to mention maybe even a few large dents. Those truckies on the roads drive like theyre in formula 1 cars, they keep spitting stones / rocks onto your car
2. You risk damaging vehicle
3. Drive for 9hrs//? Did it once, never again
4. Add to this, your fuel cost will be atleast $80
TNT transfer cars down syd to melb depot to depot from $330.