I am working on a john Deere 5575 the original problem was no hydraulics. I pulled pump and found coupler broken when I went to put new coupler in I realized the pump shaft was very worn so I sent pump out had it rebuilt I put everything back together I have all hydraulics except right side will not go forward. I tee in pressure gauge on left side I get 500 psi and if I hold lever pressure stays at 500. On ride side I hold lever pressure spikes up near 1000 and then creeps down to about 50 i do get a little jerk like it wants to move but that's it.
Welcome to HEF posrepair ! Right side reverse OK? Left side works OK? If so I would remove the two lines from the pump that go to the right side drive motor and cap the pump with metal caps (perform all diagnostics/repairs with the machine blocked up off the ground). Then when you move the lever (engine at idle) it should want to stall the engine (check forward and reverse). If it does stall the engine in both directions then you have a bad drive motor. If it stalls only in one direction check the high pressure relief for the affected direction. Maybe swap it with the side that works to check if the problem follows the relief.
Yes Right side reverse works and left side works. I was looking in repair manual it looks like it only has one dump valve per side? Thank you for help I am going to try that test.