front diff.?

[newkid17]

ok so me and my girlfriend took her SVX out today, and we were waiting at a stop light and than took a left turn, all of a sudden there was a loud thump noise, and it didnt go away, we stoped and i took a quick look at it and it sounds like it is coming from the front diff. it is a continious thud, and like scratching noises coming from it when you just coast it in nutral, but when your in drive it will hold back and al of a sudden take off and there is that continious thud noise.... i am going to look at it tommrow, but i just wanted to know if you guys had any opinion on it?
thanks,
Bobby