Im changing the oil in my transmission and the bolt I have to remove to drain is huge, i brought a 23mm but its just too small, and the next size bunnings have is a 25 which i think might be too big.

Are the bolts metric or are they imperial? and can anyone tell me the correct size, thanks.

Well i got the right size head, but it wont come off, spent 40 mins on it.

If i just drain the oil from the side plug, fill her up, run the car around a bit then drain and fill again do you this will be enough to compensate for not being able to get the bottom plug off.

yeah it's metric ie 24mm...

Get a breaker bar and/or use some innox or spanner wth the exact right sized head and give a few solid hits with the hammer.