Currently I am working on a 2000 JD 444H loader. I am having issues with the boom speed. unit drives, steers, and bucket tilt work perfectly fine. Pilot pressure at controller is within spec. I resealed both boom cylinders thinking one had leaking piston seals. no change. hoping for some diag help. thanks in advance.
I have a 544h with same problem.....I'm tempted to tear into control valve if something would be limiting spool movement......machine labors like it is pumping more oil but has nowhere to go
while operating boom up operate the bucket function and notice if boom speeds up.
NO speed does not change
No speed change on the 544h either
Check the Load-Sense (LS) Signal: The 444H uses a variable-displacement pump that relies on a load-sensing signal from the control valve to increase output. If the check valve for the boom section is leaking or debris is stuck in the signal line, the pump will remain at low standby pressure even when you pull the lever. For detailed teardown procedures, you can reference the 444H Workshop Service Manual or consult specific pressure. Inspect the Boom Circuit Relief Valve: Each circuit (boom and bucket) typically has its port relief valve. If the boom's relief valve is stuck partially open or its spring is weak, oil will bypass back to the tank instead of going to the cylinders, causing slow movement under load.
Is it the same speed up and down? Had an excavator with two functions up/down acting at wildly different speeds, was a tiny bit of debris in the section valve causing limited spool travel in one direction. It was a section of cast iron thread about 3/8 long from some prior bad repair.
Suli,is correct about the load sense signal. That is why I asked for the simple check. Sometimes if the boom function load sense signal is weak activating a loader function while raising boom will send a stronger load sense signal to pump control and you will notice a speed increase in boom speed. Please post a SR# for your loader and someone can send you the correct test procedures for your machine.
444H SR#DW444HX575230