So, to wrap this up, yesterday I was told that Mazda has not seen enough of this problem to generate a recall, the word recall was used, but they are well aware that there are a number of these bad differentials out there. Honestly, we had added 4 hours to a long day's drive home in order to pick the car up yesterday, and get it home ahead of a large snow storm coming into western Colorado today. We were trying to get home with as much daylight and as little deer dodging as possible, so I was in a hurry and didn’t ask all the questions I now wish I had. I didn’t find out exactly what is going wrong with these differentials. I did find out that there is no TSB, and no recall. This was the first one this dealer had seen. They only put in the “Mazda recommended” amount of SG1, so I will still have to fill my differential.
All in all, I live in a rural part of the state, 185 miles and three mountain passes away from the dealer. It took a lot of time on the phone to arrange the tow, at least 5 hours with Mazda US and RSA, but once things got moving, the car left here Thursday and was ready to be picked up Tuesday mid-day. I was very happy with the communication and service from both Mazda USA, and Bob Penkhus Motors in Colorado Springs. Roadside assistance seemed much less efficient, but the whole thing worked out better than expected.
Hopefully, the problem, whatever it was, has been fixed in this new unit, since I only have about a year of drivetrain warranty left.