Ford 540A 3 Point problems

Recently, I purchased a Ford 540A (1981?) industrial tractor. It is equipped with a front loader with a dedicated pump on front of engine. The loader works fine. The 3 point, however, does not work corretly. Sometimes, it will not lift, other times it does lift. To get the 3 point to lift, you move the lever to the rearward position and "play with" the draft control lever. When it does lift, the hitch raises slowly sometimes pausing. To me, it acts like not enough oil. Checking the oil in the transmission from the fill hole, if anything, it looks like the oil may be too full. The oil is dark colored. The tractor is equipped with an independant PTO. Any ideas where to start? Also, the Fast/Slow "knob" on right side of transmission housing is stuck in slow.

The 3 point on this tractor appear to be very similar to the 4600.

Here is a picture of the side of the transmission. The fast/slow know is broken off.

Being a new tractor model in 1981, I would think that the hydraulics should be the same as the 4610 rather than the 4600. I'm not that familiar with the hydraulics on that series, but there should be others on here who are. I'm just wondering if the 3 point never got much use over the years since it was an industrial model, and may have been run without enough fluid in the sump for some period of time, or with water contamination, and things inside might have gotten all rusted up.

Probably the best place to start with is a fluid and filter change. I don't believe that the transmission shares a common sump with the 3 point hydraulics on that model, but I may be wrong. If I am correct the rear axle center housing is a separate sump from the transmission and is the sump for the 3 point hydraulics.

The hydraulic filter for the 3 point should be under the left foot rest since it looks like you have the gear pump inside the rear center housing under the flow control valve. The drain for the fluid is under the differential housing and the fill hole is on top of the diffy, under your right butt cheek when you're sitting on the tractor and has a large hesx head plug. It may or may not have a dipstick on the left side near the PTO handle to check the fluid level. If there is no dipstick, then the level check should be a hole on the right side near where your right heel is when you are sitting on the tractor and should have a square headed pipe plug. I can't tell for sure from your picture, but the level check plug may be the one just below the rear of the flow control valve assembly. It's in the recess that's just above dead center of your picture.

Good recommendation to change oil and filter oil was dirty dirty. Wondering if wrong oil was used. Small particles of either brake disk or pto clutch pack...probably both were in the oil. So correct oil meant for wet disks added and new filter. The filter was barely hand tight. Surprised wasnt leaking. I suspect it was sucking air. Anyway, works correctly again. Will monitor oil condition and maybe change out the filter again soon.

Good recommendation to change oil and filter oil was dirty dirty. Wondering if wrong oil was used. Small particles of either brake disk or pto clutch pack...probably both were in the oil. So correct oil meant for wet disks added and new filter. The filter was barely hand tight. Surprised wasnt leaking. I suspect it was sucking air. Anyway, works correctly again. Will monitor oil condition and maybe change out the filter again soon.