Well you can add me to the list with a noisy rear end.
Unbelieveably I just changed rear end fluid again at 91000 miles with Mobil 1 Super/Sync LS 75/140 and within 500 miles the noise started between 50-58 mph. I even added a bottle of Ford LS additive but that did absolutely nothing to help. Looks like my first Spring time project may be an upgrade to 4:10's. That is unless I part ways with this one and get that new one I have been thinking about.

 

Marc- what do you think happened in that 500 mi.? Do you think your gears (or bearings) actually wore in that little time? Not impossible, that's for sure, but highly likely, I have my doubts. Did you use the same fluid before? (meaning M1) I know it's an expensive long shot, but I don't think I could accept that the M1 was not in any way responsible. Tons of people swear by M1 products. I have heard of too many problems with M1 products to believe they can be taken to the bank 100%. Many many stories of switching to M1 oil and burning oil and switching to another brand of Syn. and using none. What gives? I have seen it 1st hand. May be NO answer there but it's a little more than coincidental that it started the noise so short a time after changing, even if you used M1 before.

 

I doubt the M1 had anything to do with the present situation. I had changed to M1 somewhere around 30,000 miles so that is what I was replacing.
Just ruffles my feathers a little. But after 91500 miles I guess something has to go wrong. Luckily its something that can wait until Spring. Too much snow here now to worry about the noise..