JD 750 Loud pump noise?

[bobber]

Hello, I have a JD 750 and whenever the hydraulics are in the neutral position, I get a loud noise like the pump is straining. Also when I feel the pressure line from the pump, I can feel a bad vibration in it. When I move the lever to raise the bucket or anything else, its quiet as it should be. Anyone have any ideas where I should start? Thanks, Jim

 

[Captn_Dave]

I have not had a JD pump apart.... however it's quite common to have a coupler drive the pump. When a hydraulic unit is not under pressure the coupler could possibly rattle because it is worn on the drive/engaging surfaces... and when the pump is under load the slack/looseness/gap in the coupler would then be tight by virtue of the pressure on the coupler.

Just brain storming........