Put the grapes in a large mixing bowl. Set aside.
To a blender, add the sour cream and brown sugar. Whip together, just until evenly combined.
Use a spatula to stir the cream into the grapes, tossing carefully, to coat evenly, but without squishing any grapes.
Cover, and refrigerate, until chilled & ready to serve. 1 hour, no more than 3.
When ready to serve, transfer the grape salad to a serving bowl. Give everything a good stir, sprinkle with the pinch of salt, and then top with the chopped pecans.