Disclaimer, I admit I've never really paid attention to how warm a rear differential gets after running for a bit, so I have no idea if this is normal or not.
I just put a new locker and 4.30 gears in a new Strange center section into my '69 Mustang. After taking it for a 20 mile spin, and only driving with restrained driving habits, the rear seemed to be really warm, actually hot, to me. It was hot enough that I couldn't lay my hand on the rear of the housing or the center case. I got my infra-red temp gun out and the temp on the case read 197*. The temp on the rear of the housing was reading 184*.
Does this seem abnormal to you guys? Maybe normal for a rear that's just seating in? When assembling it, I went by the specs that Strange gave me and, according to their break-in instructions, I only drove it with light acceleration and no burnouts etc. Like I said, I've never paid attention to rear temps before, but since I'm taking this on Drag Week in 2 weeks, I thought I'd check it closer than I normally would, to see if there were any problems. There was a light howl at steady cruise with no load, but it immediately disappears upon even the lightest acceleration or deceleration. It seemed to act normal otherwise. It's also fairly hot and muggy out at 86* with over 90% humidity.