98 Ford Explorer wont move in reverse or overdrive

I have a 1998 Explorer with a auto trans that will try to move in revese and Drive but cant seem to get going. I can use all other gears if I manualy shift from one to another. We can turn over drive off and start off in Low 2, and when vehicle gets to aprox 35 mph manualy shift to drive, then when speed reachs aprox 45 to 50 push the OD button to turn OD back on and trans will shift into overdrive and go fine. On reverse only thing that will work on it is to throttle and get vehicle moving and once it starts rolling just keep it going. This has been going on for several months but couple months ago it started working fine and lasted until couple weeks ago and is back to the problerm described. When problem started changed fluid added LUCAS, tryed Sea Foam trans tune and nothing worked until like descrided 3-4 months later started working fine and worked for 1-2 months and has quit again. Looking for suggestions prior to rebuilding transmission.