I checked it 3 times with an IR gun.
150F after the first 20 miles, the last 5 of which were stop and go traffic
180F after the next 100 miles
added ~28oz of lube
160F after about 40 miles
drove it some more
added ~12oz today and saw it was dripping when I parked it.
It looks like I could leave the level at the fill plug minus 12oz and it doesn't seem to vent past that level. The fill plug is about level with the bottom of the axle tube (od).
I was a little upset, but I got over it. This is a good shop with a great rep. If it had been one of the others around here, I might be feeling different now, lol. But I guess we'll see how that turns out.
I read on some manufacturer site that the temp during break-in is critical as it tempers the wear surfaces. They say if it overheats the metal can soften. They also say to repeat the stops every 20 miles or so and let it cool for 30 - 60 minutes, which my guys didn't say. I guess the rule is you can't be too careful and patient with new gears. I have been keeping it slow and taking it easy, but I have not been stopping every 20 miles to eat lunch.
I'm kicking myself because when I checked those temps I noticed some lube on the ground but it was night in a filthy parking lot and I just assumed it was already there. I didn't notice it under the diff so I didn't make the connection until it was in my driveway.