In a previous thread about my gearbox linkage, I was wondering if that could have been giving me problems due to the difficulty I was having in changing gear, Anyway I decided to take the end plate off and see what happens. Guess what? between 3.5 and 4 litres 'fell out'. I filled a 2 litre bottle, 1 litre bottle and allowing for half a litre that went all over the road, that makes almost double what its supposed to have. So my word of warning is that if - like me - you fill up the gear box through the breather and wait until it dripples over the top, the chances are you have close to 4 litres in it.
I put just 1 and half litres of new oil in and what a differance it's made, I was all set for getting another gearbox.
Its a lot cheaper to learn from someone else's mistake