Flexiplate or Gearbox?????????????

I have an 1996 P38 4.6 auto which i think may have a flexiplate or gearbox issue.

To start off with when its in park or neutral there seems like a light cluncking noise from the auto gearbox.

If i rev the vehical standing still just over 3000rpm there is vibration.

I im driving and floor it ther is vibration over 3000rpm

I have tried putting it in neutral when moving and the vibration dissapears.

Any ideas to weather it is the gearbox or flexiplate??????????????????

Calculated guess (90%) it's the flexplate...either way it's the gearbox (Or engine out).

hello mate, i dare put money on the flex plate causing the vibration. when you get it to bits you will see the cracks that tend to appear around the bolts that hold the torque converter, the boxes seem to pretty good and rarely give problems of that nature.