Here is the motor valve that I have in my loader. It will feather the flow perfectly, absolutely no jumping. I can easily move the loader 1/2" at a time in low gear. I have 22 gpm to my drive circuit at 1800 rpm. I did add the center return kit to that valve to make the handle return to center. One difference is that I an only turning one hydraulic motor, your circuit is a lot more complicated.
What valve are you using for the motor feed?
https://www.surpluscenter.com/Hydra...Motor-Valve-w-Flow-Control-9-7497-30.axdIt could be the hokey way cattrac ties all the wheel motors together. I can see if one motor was getting all the flow, it would pull, then the others might try to turn and that might feel like surging. Would be interesting to hook up one motor to the drive and see if the jumping goes away.
If the valve you are using isn't a motor valve it could cause this also. A motor valve allows flow to pass when you return the valve to neutral. This would allow the machine to roll while the handle is in the center. If you had a valve made for the loader in the drive, it would shut the flow off completely when returned to center. This would immediately lock the wheels up, also if you tried to push it forward then stop, the jerking would make you move the handle back and forth making it worse.
