rear half shafts
check out the boots around the rear half shafts, at the differential side as well at the wheel side.
I had a dry half shaft on the LHS (euro - passenger) and it made a similar noise ONLY when I turned right - i.e. there was little weight on that side of the car. This MIGHT be the problem on your car as well ....
It turned out that the inner joint of the half shaft was dry. I re-packed the joint (on the car, I just removed the boot by slackening the metal strip securing the boot) and the noise is gone since then .....
it makes sense that the noise disappears when moving backwards because the force on the bearings are different (i.e. there is little wear on the races).
If the boot(s) are shot they are easily replaced - the centre bolt in the rear hub might be problematic to remove, but there is info in the archives on the half shaft and it's removal. I know the US contingent around this site calls the half shaft by a different name, which escapes me now, but someone is sure to come up with the correct term.