Torque converter whining

Hello

I have a problem with my gearbox at the moment, it sounds as if the torque converter is whining, in touch with the engine speed.

Went underneath the car when the wife touched the accelerator and it does sound as if its coming from the bell housing/torque converter area.
Car still drives but i am not doing so at the moment just in case, it is a bit rough on the downshifts though.
Changed the oil 10,000 miles ago with the proper esso lt stuff and filter.
Have had a quick check of the torque converter bolts and they are tight.
Is it gearbox replace or torque converter replace?
I have done a search and it points to the converter, has anyone had any similar problems
Its a 2004 4.4 bmw petrol with 84,000 on the clock.
Many thanks in advance
John