My new gearbox from Ashcroft's is now in and working nicely . The tragedy of it is that it should never have needed replacing . I had always had a very slight ooze of oil under the gearbox , but at every oil change I could still feel oil in the filler hole so I didn't worry about it . At some point the gearbox breather pipe had come in contact with something hot , had melted and started to block up . This must have come to a head after the last oil change , and the box gradually started to lose oil when under pressure . This might explain why it lost oil yet there was never a drop on the ground when it was parked . The result of course was a destroyed gearbox . It managed to survive to it's last 1/2 litre . So if you see even a drop of oil hanging under your gearbox , check your breather pipes and keep a very close eye on your oil levels .