tracking down whirring noise.

Hi to all,poopsie here again,still trying to nail down slight whirring noise when clutch is released on the ls3 conversion.I had the idea of putting transfer case in neutral,engine running,and going thru the gears.On all gears when releasing the clutch the noise was present except in fourth gear .This leads me to believe the input bearing is fine,the transfer case is fine,so I am thinking the preload on the input shaft has changed with the fitting of the marks adapters bell housing and input shaft extension and the noise is just the gears bedding in again.Does anyone think that this could be the noise.Thanks guys.

It could just be gear noise and it disappears in 4th cos it's 1:1.

thanks old mate I think you are right and I hope you are right,The vehicle drives great,clutch and gearbox work well.