What causes my driveshaft to "jump" in this video?

Noise on decel is either too much pinion depth or too little, I can never remember which. You might try dropping the drive shaft and see if there's any slop at all in the pinion yoke, as if the pinion nut is trying to back off. That's actually a pretty common issue. What casting is the case? I "THINK" I see "742" as the last three, but I'm not sure.