Do i need to renew my american passport to go visit, or can i travel on my australian?

Answer 1

You are required to exit and enter the US with a US passport if you are a citizen. What you do once you're out of the country is up to you.

Answer 2

as rules tell you ? since you are an American citizen , it is always best to use your nationality passport when traveling , and besides ? you may need some visas with some countries , and not with your American passport , they advise you to use only one passport when traveling
:-)