Figured it out.

Clutch goes in.. Shhhthunk whrrrrrrrrrrrrrrr.
Clutch goes out... Whrrrrrr...(spins down).

Problem suddenly was obvious tonight on the way home.  Every time I shifted, my lights dimmed until they nearly went off.  Sure enough, I pressed the clutch override button and the noise came on and stayed on uintil the truck died 20 seconds later. 

The ignition switch had shorted to always on the start position.   So every time I shifted, it would engage the starter and then it would go "WTH?" and spin up to maximum rpms since the engine was already running.    Apparently starters don't like going 2000rpm+ and sound like a throwout bearing going bad when they are forced to.  The high pitched sound like a clutch disk grinding itself at high rpms was the bearings pulverizing themselves.

Course the starter after 20 shifts or so getting home was smouldering, so it's probably also fried or close to it.  For once in my life I'm glad something broke.  At least the W56HD is in fine shape.  $200 I can afford.  $1300... yeah... got my blood pressure a tad high...


One question, though.  Apparently this is a gear-driven model.  What's the chance that it might have damged the gear in the engine that it connects into - or is it always engaged to that gear and the starter has its own internal clutch/etc to engage itself?