Oh THAT noise...
Kinda hard to describe, not exactly a whirring, not a knock, not really grinding, not exactly hissing either...
I've got the same thing, it did get a little better when I modded my trans mount by through drilling it & installing some 1/2" gr 8 bolts. (making it, for the most part, a solid mount)
These pics show the first attempt with 1/4" hardware, which wasn't up to the task.(sheared off)