Update: Shaft is at the balance shop. I noticed like 6 or 7 different balance weights on this one.

I *also* noticed that the very front u-joint at the transmission flange was a little stiff in one axis. A few taps on the joint loosened it up, but I doubt that was the whole problem.

I just want to vent a little about how HORRIBLE the design is on that front flange set of bolts. There is literally no clearance to move a wrench on the nut, which is what should always be moved to break a nut/bolt interface loose. The nuts barely even have room to move, in fact not even 1 whole flat. On top of that, it's only possible to get an open-end wrench on anything in this setup (maybe a flare wrench would work) and only in one orientation. I'm using socket-head hex bolts for reinstall.

Will post an update when I get the shaft back.