My brother has a 1986 Ford 1210. Recently it has developed an issue where the 3PH pulses up/down slightly when there is a heavy load attached like a 6ft rear blade. It is most noticeable when the hitch is raised to the half-way point. It will sit there and continue to raise and lower by about an inch or so. It does not exhibit this condition when the hitch is raise all the way or lowered all the way. It also has to have a certain about of weight on the hitch to do it. The 250+ lb. rear blade will do it but a 200lb person on the hitch will not.
It's been almost 200 hrs since the hydraulic fluid and filters have been changed.
I would also be interested if anyone knows the details on the hydraulic filters on this tractor. Looking at the parts listing it appears to have three filters. A main spin-on filter on the left side of the engine, a filter cartridge inside a bullet-shaped silver housing on top the hydraulic pump, and a suction screen filter located on the left side of the rear axle housing, just inside the rear tire.
I've include photos of the filters below.