I'm not thinking a sprag is the issue. They either hold or they don't. Not holding usually involves some crunching of the parts. Both the Int, and high clutch are fed throught the center support. Just trying to link the problems. Does the 1/2 shift act the same when manually shifted? If the kick down solenoid were loose, it would result in no forced down shifts, as the solenoid is held open by pressure, as the throttle moves down the voltage is incressed to the solenoid, when the solenoid overpowers the pressure and closes you get a forced down shift. A stuck on solenoid would result in very high shift points, but you would still have a shift.
Steve have your friend call me, might be easier to help him with a qyick phone call, I will post any results and findings back to this thread.
Dan