The photo in the previous post 19 looks like an AA truck under/over unit. These are not overdrives but low to high splitter auxiliary units. It has an underdrive and a 1:1 ratio. https://www.fordbarn.com/forum/showthread.php?t=244077
There are likely other units that give under/over auxiliary action for model As but most are for trucks or model Ts.
This is why I asked.
If it has a planetary gear set then there could be a problem there too. Not enough information can make for a lot of guess work.