Rear Sure Track Binding

I have a 2000 xj with a 4.0 auto trans, np231 transfer case and Chrysler 8.25 rear with 3:55 gears..So recently around slow turns and sometimes going straight I hear my rear binding up and its been slowly getting worse, I changed the fluid and added friction modifier and no help..is there any suggestions on what to do? Money is tight and don't want to waist any. Should I buy Mopar fluid for the rear and Mopar friction modifier ? Or is the rear shot? Any help is greatly appreciated ...
Thanks

"hear my rear binding up". what does that mean? What does that sound like? How do you know it your "rear"?

Is your rear a limited slip? If not, why would you add friction modifier? When you changed the rear end fluid, was there any sign of metal wear?

Need more information to assist you.

I can feel it bind on full turns ...and I'm positive the noise is coming from the rear, also like I said its the sure track which is the limited slip...when I change the fluid there was not one piece of metal in there...I just am not sure if I should fix the limited slip or if I buy the Mopar friction modifier it would help.

so this was a problem before you changed the lube? you could try the Mopar additive just in hopes of not wasting the oil in there, but if you added the additive already and you are still having problems, it's likely you have a mechanical issue.
if the L/S is wasted, the easiest fix really is to get a used axle and swap out the whole thing.