Engine/Gearbox rumble low end vibration

Any ideas, shed light etc on 1600 engine/gearbox low end rumble or vibration.
The engine has been fully reconed, there's nothing obvious banging the chassis. It's an oscillating sound/vibration which when you hold the gearbox around the bell housing you can really feel. This transfers into the vehicle as a constant thudding vibration. There's no end float and I've had the engine out twice to check that the flywheel is torqued up correctly.

T

 

Does the noise go away when you drive it?

TBH it's either going to be the box or engine, but without experiencing it first hand, then it's going to be difficult to pin point it!!

 

The noise is there when either stationary (but increasing the revs) or moving when in gear or under load.

? Flywheel inbalance

 

lay shaft bearing(s) in the gearbox...


who rebuilt the engine?

 

The engine was rebuilt by an air cooled specialist in Manchester

 

There is no difference in the vibration noise when the clutch is pressed

 

I would've said flywheel as a poss, but you've checked that.

 

Take it back to the air cooled specialist in Manchester?