General Discussion

I've searched and can't seem to find any of the old posts I know were here on this subject so...

My port transmission started to drop pressure more than typical last year. It would hold steady at 320 at cruise, but drop to ~275 on shift. This year, the pressure at cruise varies from 270-350, sometimes at 320. It wanders. As a first step the oil was changed and the intake filter cleaned (it was reported there wasn't much on it after at least 10 years. The oil was clean, no smell, no metal, etc. The filter had a bit clutch pad friction material (I forget what I was told it was), but the amount was small and not surprising given the age and time between screen cleaning. For reference we put ~50 hours per season on the boat.

After the service - pressure still wanders, not going quite so low during cruise, but still 290-350 and shift is dropping to around 200 (I need to verify this, was rafting to another boat so it wasn't my prime focus).

Thoughts as to what this could be? I'm thinking the pump is okay since it's hitting 350, but what causes the high pressure? Something in a return line maybe?