In a large bowl, beat together cream cheese, sour cream, granulated sugar and salt until smooth.
Stir in vanilla, then fold in grapes.
Transfer to a serving dish.
In a medium bowl, stir together brown sugar and chopped pecans.
Sprinkle brown sugar mixture over grape salad in serving dish.
Serve immediately, or store in the refrigerator until ready to serve, up to 24 hours.
