[o6r1man]

Update: I drained the diff fluid and filled it back up with valvoline 80/90 and the ford additive. I drove it about 3 miles and it chattered a few times when I first set off, which I expected. I got to a big parking lot and did the 10 circles each way, I would say it is 99.5 better so far. I will get some more miles on it tomorrow and see how it does...