If you have Reverse then you have a broken band. It will drive in third by holding the lever out of N but not quite into D till the fault lights are activated. No Forward or Reverse may be selector cable popped off. If so the selector will like its not doing much.
mags
March 2011
I don't suppose that you have checked the transmission fluid for a while, if ever?
DB
March 2011
Automatic Answer
We may have found other answers which could help you.