I got trans problems with my newly acquired 86 420SEL. Reverse in all positions.

I have removed the valve body and cleaned it up a bit. Made sure everything is moving. Verified the shifter is actually working properly and engaging the valve body. I have no history on this car so I don't know any symptoms up to this.

In drive it is has both reverse and forward working against each other but in all other gears its reverse.
Trans is going to come out, because the park pawl is messed up but it would be really nice to know where to look to find this problem before I open it up. I have some parts left over from an earlier trans surgery.