644j loader all of a sudden lost almost all hydraulic functions. Some of the power will come back after letting the unit get up to 120 degrees of hydraulic fluid temperature, but it will not have 100% power. Hydraulic fluid has been changed and it did not seem to help. Unit will shake if you increase RPMs and command maximum hydraulic on any ram. We tried disassembling the main distribution block and soaking it but that didn't seem to change anything, although we have noticed that tapping on the distribution block can help get the hydraulics working somewhat. On the distribution block which is right below the control levers on the right side of the machine, we've tested the hydraulic pressure and found it too jump around from 450 to 600 PSI sporadically, but when it's cold and host started up the distribution block only shows 100-150psi. Not sure where to look next. Has anyone else has an issue like this with this machine or similar machine?
My 544J needed the main pump replaced around 5k hours due to the stroke piston (the thingy that makes the displacement change) sticking in the bore, resulting in low pressure after 3 seconds of running. Come to think of it, my WA270-7 had main pump replaced for the same reason.