L555 can roll *almost* freely when off

[chrisepp]

When the L555 I have is off, it can roll almost freely, on both sides. Just a *slight* incline and it will start to roll if it's turned off. You can feel/see slight hesitations evenly spaced as it goes.
What would cause this? I don't believe that is normal. This is a used unit I got and am fixing up.

 

[Dirty70Bird]

I suspect the pressure relief valves on the hydraulic pumps have some dirt in them. There are 4 of these valves, 2 / pump. They are located behind some large hex caps 1 3/16 IIRC. I have a similar issue, and have recently figured out a way I might be able to disassemble them to clean them properly. I have had them out of my machine, but to disassemble, you need some magnification and small snap ring pliers, and 3 different o ring seals. I do have an exploded diagram of these pressure valves that I could send. The o rings are standard size o rings and cheap at a hydraulic shop. Otherwise replacements are available for around $300 each.

 

[River Fluid Power]

When the L555 I have is off, it can roll almost freely, on both sides. Just a *slight* incline and it will start to roll if it's turned off. You can feel/see slight hesitations evenly spaced as it goes.
What would cause this? I don't believe that is normal. This is a used unit I got and am fixing up.

If your machine slows down when hot, you may be looking at internal wear. This can lead to loss of preload in the pumps and/or motors, which can cause it to become weaker when hot. It can also cause the "runaway" problem you are having. In some cases, it can even happen when going down grade with the machine running. The even spacing you are describing is most assuredly being caused by something that is unseating under pressure, and reseating after the pressure drops. It would happen faster than you can say what is happening. The unseating could be from lift-off in the pumps or motors, or from the relief valves allowing oil to bypass.