John Deere hydraulic problem

Hi, I have a 1989 John Deere 510c 4x4 backhoe. I bought a new hyd pump for it and installed it. It worked fine for a several hrs but then the steering got stiff, only the steering. A day later the levers for the backhoe are now very tight. It sounds fine and and has plenty of hyd. power. Just the controls have tightened up. Definetly not right. When on of the control levers is moved, it will often get stuck and taks a bit of muscle to snap it back. I called the company where I got the pump and they said the pressure on the new pump is set too low and I need to adjust it. Would low pressure cause this? I have had machines for many yrs and have never had low pressure do this, but first time for everything.



It has pump # RE33603.



Thanks very much,

Matt