dashco,
Sounds like you have a serious problem. I'm no transmissio guru but I have a few ideas.
Check your TV cable. Does it move freely?
Does the transmission have enough oil?
Will it move at any RPM in overdrive? If not then its a serious problem. A valve may be stuck in the valve body.
Check the linkages from the lever to the transmission. You may have a loose lever.
Did you some type of maintenance before this problem? Or did it just start up one day?
------------------
Gerardo
1983 Custom Truck
TX Plates: "BAD BOW"
http://www.geocities.com/abetterchemist/