Oh dang. I gave it a closer inspection and the inner left tie rod end is indeed toast. At least half an inch of axial movement when I wiggle the wheel, with zero attending movement of idler arm or center link.

I raised the car off the front left wheel and it has the tiniest bit of 12-and-6 movement, small enough that I can't see it but can feel a tick at each extreme. Could still just be the tie rod, I'll report back after I've replaced them this weekend.

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RIP:
2011 E350 BlueTEC, Schwartz 81k (totaled by uninsured drunk driver)
1964 Unimog 404.1 (wrongfully towed by the city)
1994 E320, Brilliantsilber 208k (transmission shuffled off after sudden catastrophic fluid loss)
1982 300D, Silberblau under a blue repaint 256k (sold for parts)
1995 E320 Polarweiss, 131k (sold for parts)
1995 E300D Polarweiss, 287k (totaled by drunk driver)