The open hole at the end of the Input/Turbine Shaft is the Lube Feed hole that feeds the Output Shaft than onto the Geartrian.
There shouldn't be any cross leaks between it & the 3-4 Piston feed hole.
Lube is fed from the cooler return through the pump, Then through the stator support, Then through the hole in the picture. Then travels through the Input Shaft to the open hole at the end.
