A good number of the older tractors did not use hydraulic oil, it was gear oil as the pump and oil were in the transmission/rear end case, often the pump is worn lots and hydraulic oil is to thin. Poor control of the 3 point is in part thin oil, worn pump, and worn control rods, levers, springs etc. in the case.
One of the worse killers of the hydraulic/3point pump was the oil filter/screen. It is often on the pump or a tube running lower in the case, the screen had a "steel" mesh covered by a fabric?, the steel mesh would/will eat up, rust away, and bits of rusty steel, fabric, dirt etc. go through the pump along with the so called "oil".
A lot of water could get into the oil, water, rain, snow melt runs off the dash onto the gear shift lever and into trany case. Rubber boots last seen 40 years ago. A certain amount of dirt etc. also enter this way too, in hand with not cleaning quick connects if used. I often drained litres of water out the old girls, followed by"oil??" that was "rotten". The replacement of the pump, filter, oil, often returned an old worn out tractor into a old worn out tractor with near new hydraulic systems and somewhat worn controls.
Dam, the fun I had!
Just seen Dan Dubeau's post, remember how to use 4 wheel drive, keep it in 2 wheel drive, then when your stuck, put it in 4 wheel, back out and go home! Remember, 4 wheel drive gets shuck, life gets interesting, in hand with remembering what neighbours have bigger tractors and long, big tow cables!