I have a t50 5speed and cant get the speedo drive to stop leaking. Its only just started happening recently. Replaced the o-ring and the cable itself to no avail.

Is there something im missing in the sealing department? The single o-ring doesn't seem like an effective seal for the cable.

My next theory is if the box has a breather? Im assuming so and its blocked because the oil leak only appears after a few days since topping up the box. Thinking its possibly building pressure and exiting via the weakest link.

Any suggestions appreciated.

Cheers

Yes, all gearbox I seen have a breather. Should be near the top of the side somewhere.

Older Datsun boxes had a simple bent tube, newer ones have a white round thing over the tube.

The box may be overfilled, what I would do is remove the filler plug and let all the fluid run out.