the rear end in my 88 has started making a grinding noise only when I turn right. I have replaced outer wheel bearings added friction modifier. Could this be the limited slip
Mine did that when I first got it, haven't turned right since.
You had the drums off so you ruled out brake shoe problem, and you didn't see anything in the old oil? C clips didn't have any scoring? How many miles on it?
I rebuilt the drums with all new parts and didn't find any metal shavings in the oil but there was some scoring on the c clips on one side. It almost feels like the splines are slipping but I don't have a lot of play when I move the wheel with the car in the air. Don't know anything about lsd's or the clutches