My '01 supercrew seems to have some issues. When the truck warms up, after driving 15-20 miles, and I turn a corner, there is a whining/grinding sound that comes from the rear end of the truck. I had a leak in the rear seal awhile back, had it repaired and the synthetic oil replaced, but wonder if there is additional damage. When I come to a stop and turn to the right, the truck "chatters" as it turns, so I am wondering if it is the Ring and/or Pinion, or perhaps a bearing that is worn and ready to explode when I am on the interstate next time??
if it was just the chattering yes i would say it is just the limited slip, but since you also have grinding there its hard to tell. i tried adding just the tube of modifier with no luck i finally had to tear the rearend down and buff the glaze off of each clutch. i would start with taking the pan off the rear end and see if any metal shavings come out or there are any noticible problems. good luck