You should check the level at least once a year.
To do this. Go for a drive from Cold for around 10Mins or so. Dont give it too much. Just drive it normally.
Go back home. Put the car into Park and Put Hand Brake on. Leave Engine Running.
The car must be on a level ground. (The Trans Fluid needs to be around 30-50Degrees (No More or No Less). Thats why you only drive the car for 10mins or so.
Grab a Number 14 Spanner I think. or 15. Somehow you need to slide under the side of the car and undo the Trans Sump Bolt which is located on the Rear under part of the Trans Sump. It wont drain your trans as it has a tube with that sits at the full level of the fluid.
You should get a slight trickle of fluid coming out. If you do, put the bolt back in straight away. The fluid level is good.
But I must say, its a bit of a prick as there is not much space to slide under the car. If your a skinny person, should be OK. And also you can burn yourself on the exhaust (In my case).
I though next time I might jack the front and rear of the car up at the same height which might make it easier.
IMO Holden should have put a Dipstick for the trans. All they had to do was put a lockable Dipstick to prevent tampering under warranty. If the lock is broken, it voids the warranty of the trans.
At least after warranty has ended, you can break the lock. Mercedes had this same principle.
The only reason holden never put a dipstick was to prevent people from putting the wrong fluid in, or overfilling it, as most people dont know the procedure to check and fill the trans.
Not for Engine Bay fires. Thats just rubbish. This never happens with other cars so why should it happen to Holdens.