To all who have responded - thank you for your input! I did some research on automatic transmissions in general and torque converters in particular and now have a much better understanding of how they function.

mik15 - thank you for that information. That is exactly what my transmission is doing. Everything works perfectly fine except shifting from first to second when I give it enough throttle to rev over 5k in drive (not sport). Under less throttle, the shift from first to second is perfectly fine. So aside from suspecting that a loss of fluid pressure is the culprit, no more specific cause was ever determined on Skiper's transmission?