For those who don't know where the filler and drain plugs are on a BA sedan. They are in a mongrel of a spot. The filler is a bit hard to get to.
You will need an 1&1/8" socket and ratchet for the filler plug, and a 15mm spanner for the drain plug.
In the pics, the drain plug is at the very bottom of the photo, not a very good shot, you will get the gist of it. The filler plug stands out nicely, it has a tag on it. Holds about 1.7lt of oil.

 

 

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BA Falcon sedan diff filler & drain plugs. 001.jpg [ 478.55 KiB | Viewed 1444 times ]

BA Falcon sedan diff filler & drain plugs. 002.jpg [ 384.83 KiB | Viewed 1001 times ]

Wow, I'm glad I didn't change my diff oil myself lol.

bah its not that bad. you should see the transfer case filler on a V6 escape if you think thats bad.
Or the filler plug on the front diff of a territory.

Also on BF sedans it changed from the imperial socket to a metric 32mm socket.

Another hard one to get to is the front diff filler plug on the lastest model Toyota Hilux 4WD.