I have a JD 2940. Hydraulic fluid is good, but when trying to operate lift, it jerks or doesn't work at all. the steering is very hard to turn at any time.
Double check the fluid and after that the filter. Filter is a biggie. If that dont work you need to get a manual and test the hydraulic system pressures to isolate the problem. Could be a pump issue. There are screens in the pump valve ports that can get clogged or broken, causing valves to get stuck. Get a manual for the diagrams.