I say use a Manual transmission.If you know how to drive a manual( its a game who cares)It is alwayse best to use it.
I say this because on take off you have a lot more control over the traction of the car(theyre a powerful car if you dont take off right you will just sit and spin in which a ford will devestate the rear end of your Commodore)also on cornering instead of letting the auto take control and spin ya into a wall.
For example on the first corner of Sandown it is best to hit it between 120-160 kmh(depending on the conditions) it is better to stay in low 3rd than high 2nd I say this because if you hit the corner going just that little bit fast ( easily done comming off the strait in top gear and all)and the rear end starts to slid it's easier to have about 2000RPM of power over the in 3rd than 0RPM in 2nd.
If the rear end starts to slid out just give it a little boot and pull it back into line( whatever you do dont brake and never handbrake).
Also if you hit a corner going to fast instead of locking up the brakes and lossing all your stearing and finding your self shaving a wall for a half a KM you can just drop it back a gear it will lock up the back brakes and yes you will have stearing and as your going sideways around the corner if you over stear a little bit to much just drop it up a gear and give it a boot and pull it into line.
I love this game and if you learn it you will to. So enjoy its the closest we have to the real thing for now :-)