(quoted from post at 16:35:00 09/01/20) Is that a drawing you drew yourself, or did that come from FNH? I don't recognize it. If you drew that, I'm afraid that you misunderstand
the theory of power beyond and why it's needed.
In the drawing, you show the outlet of the 3rd valve returning to adapter plate, presumably to power another downstream function (if that
were not the case, then one could simply run the outlet of the 3rd valve straight to the return port). If true, the 3rd valve HAS to be
power beyond capable, because any downstream function will subject the exhaust core of the 3rd valve to system pressure, which most valves
and spool seals cannot handle.
All of this discussion hinges on whether or not the factory remote valves are upstream or downstream of the adapter plate. I was always
under the impression that they were downstream, hence the need for a PB valve upstream.
If the factory remotes are truly upstream of the adapter plate, then there would have been no reason to include a PB fitting on the adapter
plate - the return from the loader valve could have been simply dumped into the return port. However, since, as I contend, the factory
remotes in fact are downstream of the adapter plate, a PB port on the loader valve is definitely needed.
I'm scheduled to visit my local NH dealer tomorrow morning regarding another matter on a SOS trans. While I'm there, I will hunt through
some old service bulletins and try to find the instructions for the #9613790 tapping manifold. As I recall, they were pretty thorough,
including the theory of operation. I'll report back what I find.