450() power steering.

[Cle Elum John]

The power steering on one side of crawler is not working. It will still steer and brake but it takes a lot of force and a lot of stick travel. The clutch release and the brakes are all adjusted per the shop manual. Before I pull the unit has anyone else had the problem and found a fix. I am not really sure how it works. It's hydraulic so the first thing I will look at is seals.

Any thoughts or suggestions? Anyone know of a good functional schematic for the unit?
Thanks
John

[Cle Elum John]

I found some service information in a revised shop manual for the 450(). I have a little better idea what is going on but still have questions. I am hoping to get most of the parts I need before taking things apart.

Questions:
There is a flow divider which feeds oil from the pump to active steering cylinder. Unless the steering pump is badly undersized, how does this really help? I could not even find the divider in the online JD Parts Manual. Are there any replaceable parts in it? The problem could be that the divider may only be diverting oil to one steering cylinder.

The steering cylinders have a set of soft seals that I can probably get down at "Seals-R-Us" aka Omni Seals in Seattle (a great store). The JD Parts Manual says I can get the whole Kit for $50 a side (AT27076). I suspect I can get the whole set as pieces cheaper locally. The one thing that is not in the Kit is the valve Seat, Part number 13, T24782, ref Page 45-16. The JD price is $50 each. I am thinking this may be like the seat in a control valve and available locally. Does anyone have any information that would help me identify it and locate one at a reasonable price? Also is this generally a part that needs to be replaced? I was surprised it was not in the AT27076 kit.

I will rummage around a little in the message board and on the web a little more.

Thanks
John

[Jim B]

When a lever is pulled the flow divider moves to partially close off the flow to the opposite steering valve. Restricting the flow to the unused valve causes the system pressure to rise in the valve/cylinder being used. If that did not happen the oil will take the path of least resistance which would be through the unused steering valve and its return to the tank, resulting in weak or no steering assist on the side being pulled.

The flow divider valve is shown on the page with the steering boosters and support. It is shown at the left of the drawing, item key # 23.

https://partscatalog.deere.com/jdrc/sid ... gId/200191

[Cle Elum John]

Jim
You confirmed what I was thinking with the divider. It may have been a band-aid to compensate for an undersized power steering pump. I guess it works so I can't complain.

Thanks for pointing out the location of the shuttle valve in the parts manual. That got past me. It doesn't show any replaceable seals, that helps with the rebuild. One less item to chase down.

Do you have any ideas on the valve seat? It looks like it may be a seat used in a control valve. I will take it down to Omni and see if they can match it to something.

Thanks for the help. It is appreciated.
John

[Jim B]

I don't think the flow divider is compensation for an undersized pump. It is a way to control an open center hydraulic system to allow the use of the two steering valves simultaneously, if needed. It also can give smoother engagement as the flow divider moves to restrict flow and increase pressure on the chosen side.

I expect the seat is not in the kit as it likely does not need to be replaced very often. You might get lucky, and they can match it up, but it won't surprise me if you find it is proprietary to JD.