Sorry, I have checked those stuff before. Universal joints are still brand new. Driveshaft has been balanced.I can drive even 140km/h on the freeway and there is no vibration in the gearlever or the back of the car.And I have also replaced a couple of months ago the gearbox mounting as it started to get brittle due to age. First gear the Datsuns don't have much speed, that is why in first gear you can clearly notice the vibration on the engine.That tells me it cannot be drivetrain as it is not even at a decent speed. Thanks anyway for the reply.