Moral of the story, don't work on the car with a hangover!
This morning I ended up putting 5L of oil into the box of a pre face lift Classic WRX wagon, doh! Car wasn't on a level so was obviously reading wrong on the dip stick causing me to question my maths - no harm done (I hope!) since I'd only driven 100 yards to the local garage - but it's made me wonder what's the maximum amount of oil you should use, how much over fill to cover 4th? I'm guessing it's less than a litre - and more importantly what might have happened if I'd not realised ... would it take out the oil seals?

 

I suppose if the system pressurises then it could but not sure.

 

Well, syphoned out the excess but thought it worth commenting that when the gear oil was overfilled after a trip round the block I looked at the dip stick and it was quite obviously aerated - so I guess a good indicator of an overfill is bubbles in the oil!

 

over filling the gearbox on a classic is ok (i used 4 litres), the extra oil protects 3rd better. 5 litres is too much though