Hey canadakid2,
I'm an aussie now living here in Toronto so have done the LAX shuffle quite a few times.
As you'll pre-clear US formalities at YYZ, the transit at LAX going to Oz is really easy - a bit more of a pain coming back to Canada though.
At T4 at LAX you just need to catch the airside shuttle bus to go to TBIT which avoids having to go through security again.
Details can be found at http://www.qantas.com.au/info/flying...rportGuide/lax

A dedicated complimentary shuttle is available to connecting passengers flying on Qantas. Passengers connecting at Los Angeles to travel to Australia and New Zealand will be able to transfer from Terminal 4 (T4) to the Tom Bradley International Terminal (TBIT). It will operate daily from 4pm to midnight from gate 44 in T4. This will eliminate having to pass through security a second time. Passengers who wish to exit the terminal will also have that option.You can also walk between terminals by following the directional signs.
Tom Bradley International Terminal and Terminal 4 are adjacent to one another.

Have a great trip downunder mate!!!