hi .... its the gear boc of the mark 4 , the breather is at the top of the box right onto the gear box mount , you would think there was to much oil in it , lucky if there is 2 litres , but now loosing a lot so lucky if there is a litre lol ... no leak from shaft seals as i done them b4 it went in ..... never heard of this prob b4 , like the box is building up pressure