Time for a rebuild 2 stage pump and maybe a valve if that is the original. with the 6hp motor that would dictate a 11 gpm 2 stage pump. Might need a new pump to motor coupler. Pump at Northern Tool $130, valve $100 ( 1/2" ports ) pump is likely 1" intake port . Return line filter assembly would be highly recommended Likely under $100 ( didn't look that up) as I do not see one on there. Getting the system flushed out is mandatory to remove those metal chips. Larger tank would not hurt if so inclined. Likely another $100. Guess it depends on your abilities. Box stores usually run sales about now on a new unit sometimes as low as $750.
My old splitter lost all power, flushed all hydrolic oil and is full of metal shavings. I believe its a Didier. Had a 4hp that died, put a 6hp briggs on. I think the hydro pump is shot. Looking for info to make a 2 stage and probable a tank size upgrade. Maybe a manual? 
