Rubbing noise in rear driving me nuts

[BIGJB]

I have an Au Fairmont Ghia with an irs rear end. It has a rubbing noise coming from the back that I can't put my finger on. It sounds like a tyre rubbing but its not. It only happens when turning almost full lock at very low speed. It doesn't appear to be there when I gun it in a straight line. I replaced the discs the other day so had a good look while it was in the air and am darned if I can find the problem....all looks good under there.
It doesn't sound like metal grinding which is wat I would expect if it was internally within the diff. I have no knowledge of how traction control works so I'm not sure if that could be causing it, although the noise is there wether it is on or off.
Any ideas ppl?

[Tech Trainer]

If the noise occurs at low speeds (car park) and turning it is the LSD (yes some cars have LSD and traction control). The diff will need an oil change with the correct spec oil and an additive. If this fails to get rid of the noise you will require a diff rebuild to rid you of this lovely noise.