Well another funny story, turns out the rear trailing arms have been loose. Finally got round to checking the viscous coupling and the axle moved, coupling is fine. Tightened up as is and it looks like they are not set right. The diff flange is angled up towards the transfer box. I need to make some spacers to in effect lengthen the trailing arms to make the props parallel. This will hopefully sort out the vibration. So many things wrong with this hybrid, surprised its holding together.......