I noticed a squeak that started mid-run today and got slightly more prominent by the end of the run. I may have another failing diff pinion bearing. I ended up using another cheap bearing when I replaced the first one that failed, because I didn't have the fancy ceramic bearings I wanted to use in the size I needed. Shimming the rear diff pinion propshaft seems to be helping it, whereas the front diff pinion propshaft is getting a little wobbly, so I suspect it's the front diff pinion bearing that's failing this time. I didn't notice drive cup being hot after the run, unlike when the rear diff pinion bearing failed, so maybe it's still fine, I dunno.