"That," I said, "is definitely the driver's side axle u-joint, just as I expected." But to check myself I went over to the passenger side and tried turning that wheel, and it rotated smooth as butter, thus confirming that the problem was confined to the driver's side.
Turned the truck around and went for the jack, then said, "No! Here's a zany idea--why don't I go buy the part before I take the truck apart?"
Went and got the part, came home, parked it, started work.
Once I got the axle out, the extent to which the u-joint has died was pretty obvious:
Understand, that in the position the axle is sitting, there, it should be drooping. It is not drooping because that particular axis is completely seized. It rotates freely around the vertical axis, but won't move around the horizontal axis.
Began work on getting the thing apart. Rusted as it was, I hit it with a wire brush, and hosed it with PB Blaster; but even so, when I finally managed to get one pair of retaining clips off and came up for air, I realized that it was now 5:30 PM. Okay, the autumnal equinox is Saturday; the sun sets at 6:30 and I wasn't even well started on this shit.
The last time I tried changing a u-joint it took me two days. I have to go to work tomorrow, so I reluctantly reassembled everything.
Plus side, I know what it is, and I don't think it's something that will blow up on me.
I wonder what a shop would charge me to press the old joint out and press the new one in?