rear axle making noise?

I have this noise coming from what sounds to be near the rear axle when I have an increased load in the back like an extra passenger or something. Now the rear leafs are really shot (actually almost inverted) so I wonder if it could just be part of the tire (tires are 29" w/ no lift) hitting part of the fender or body or something. I only notice it with extra weight in the back and when accelerating from a stop. It's like a repetitive clicking sound that seems to go away around 15-20 mph. Any ideas? I am just worried because I have a 3.5" RE lift and 32's going on in a couple weeks and if there is something wrong with the crap D35 then I am really worried about it handling the 32's. I was thinking of just putting a 8.25" in when installing the lift, but don't have too much extra $$ right now. Any comments/suggestions?