Hi Tony,

The NCT testing manual makes reference to oil leaks from the transmission, which includes the gearbox. The driveshafts connect into the gearbox and hence a leak from the interface is likely to cause the car to fail its NCT. Saying that, the manual mentions 'continuous dripping' so it probably depends on how bad the leak is on the day of your test.

We'd advise you to get it fixed, regardless, as it could lead to more expensive long term damage to the transmission.