John Deere 310C reverser problem

Greetings this is my first post.I recently purchased a 1989 310c with 4970 hrs.It came from a county shop with all service records and a complete service manual.I had put only around 40 hrs. on it and it stopped going in forward.I found the oil screen on the reverser was plugged with very fine black material.I cleaned the screen and the hoe ran great for around 80 hrs.Now it,s doing the same thing.Reverse seems to be normal.I checked the screen again but it was fairly clean.When I shift to forward in any gear it seems as though it wants to move but there is no power.The clutch disconnect works properly in reverse and also seems to work in forward.I checked the F N R linkage and it also seems OK.I removed the reverser control valve and visually inspected it and saw no physical defects or sludge plugging any of the ports.While I had the valve on my work bench I hooked up the clutch disconnect solenoid and applied 12v.The plunger seemed to activate the spool in the valve.I did not disassemble the valve itself.This backhoe had all preventive maintenance such as fluids/filters performed on it during it"s life and when I drained the fluid from the reverser the fist time it seemed relatively clean with no burnt smell.Both times this failure occurred while I was spreading dirt I had excavated from a pond I'm enlarging.I was working in 2nd. gear mostly and wonder if that was part of the problem? I have two questions,first is there anything else I could check before pulling the reverser,second if the reverser needs to be rebuilt is this a project that would be beyond a person with normal intelligence and patience with a garage to work in and basic mechanic tools and a service manual?I would appreciate any advice or thoughts regarding this.