Morris Minor Owners Club

I wanted to check the oil in the diff but im having a lot of trouble trying to get the bolt undone.
I have a square socket but it just wont undo.
I have even put my impact gun on it without luck. Any ideas please.
I have been lying on my back under the car so there is not much leverage. And I just have a cordless impack gun.
Should I heat up the area around bolt.
Just cant believe it would be so tight.
Thanks Will

The plug has a tapered thread and can be overtightened to the point of being stuck.
Just keep at it with the rattle gun - it will move eventually.
I would advise against putting heat to the taper plug as you could addle the oil inside the diff.
Phil