5kTQ dragging and clanking

[Scott Oliver <soliver@gcwf.com>]

My 87 5kTQ (new master cylinder, nearly new bomb, stainless steel
lines) has developed a new malady:  turn sharply and go up or down
(i.e., drive in or out of a driveway).  I can feel something starting to drag,
as if the brakes are being applied lightly,  and then, 3 to 6 feet later,
there's a loud metallic CLANK and the dragging disappears.  It only
happens occasionally, but it's always when going in or out of a
driveway.  Hot or cold brakes makes no difference.  Diffs lock and
unlock normally.  Can't tell which wheel(s) is affected, or even which
end of the car it comes from.  The clank is LOUD--people walking by on
the street turn around.  My (good) Audi mechanic has no idea.

Anybody ever had anything remotely like this?  Anybody ever have a
caliper that would freeze against a rotor and then release?  A diff that
would lock spontaneously and then unlock?  Ever heard of a defective
stainless steel brake line with an occasional 1-way valve?  Do the rear
diff mounts on 5kTQs ever fail, like the 4kQs do? (But aren't those clunks,
rather than clanks?)  Subframe bushings (but why the dragging first)?

Completely stumped.  Ready to sacrifice to the gods, but need some idea.
 Any thoughts or experience would be greatly appreciated.

TIA,

--Scott