Locked. I'd bet a donut on it.
You need may or earlier- usually, there have been a few floating around with a 6-2x date that have been bench-unlockable, or at least, Marin claims that. Neither Jeff nor Mikey have ever seen it.
We drag guys have a fix for this, actually.
We just pop out the freeze plug on the top of the diff, tap the hole with, and run some steel braided AN line up into the bumper with a filter on it. Can stay "over" filled, and no more leaks.