Gresen 550

[oldnslo]

VA,
The reason the loader will drop with the engine of is that now you don't have any pump flow adding to creating back pressure in your system. This added flow is also under pressure as you noticed by the FEL raising slightly.

example: Numbers are for reference only

With valve in spring center condition the pump flow goes from pressure to tank. For this example lets say the tank back pressure is 200 PSI with 10 GPM pump flow. Now lets also say that lowering the loader adds another 10 GPM. This increased flow rate from 10 GPM to 20 GPM would effectively increase the back pressure from 200 PSI to 800 PSI.

Does this help explain why a restriction in the tank line would cause the lowering speed change with the engine running Vs off?

I did see some old pictures of 550 valves for sale while doing google searches and they all had the port closest to the handle plugged. I tried looking through some of my older catalogs and I didn't have any for Gresen or Dana Gresen valves.

Yes companies make some strange castings and spool arrangements per customers requests. This may be one of them. Any good hydraulic valve repair shop should be able to provide you with a hydraulic flow schematic of that valve.

Replacement valve and some Oliver green and most people would never know it wasn't original equipment.

 

[cropduster69]

Having a similar issue on my 85 chevy c60 dump truck. The lift cylinder is SA with "built in reservoir". The valve is a Gresson valve, but cannot find any model number. With PTO engaged, bed lifts great, but when move selector lever to lower bed, bed only stops its up travel, and this is with the pto still engaged. As it is now, to lower bed, must disengage pto and then select the bed in the raise position and the bed lowers just fine. Hard for me to think this is correct plumbing. Any thoughts or suggestions would greatly be appreciated,

 

[cropduster69]

Having a similar issue on my 85 chevy c60 dump truck. The lift cylinder is SA with "built in reservoir". The valve is a Gresson valve, but cannot find any model number. With PTO engaged, bed lifts great, but when move selector lever to lower bed, bed only stops its up travel, and this is with the pto still engaged. As it is now, to lower bed, must disengage pto and then select the bed in the raise position and the bed lowers just fine. Hard for me to think this is correct plumbing. Any thoughts or suggestions would greatly be appreciated,

Also, this type of lift cylinder is serviced when extended or retracted? The service port is simply a "hole" in the top of the piston end of the cylinder. Raining just now, but will get some pics to help ID what valve this might be.

 

[J_J]

Here is my take on that valve.

If a DA valve is used with an SA cyl, some people plug the A port or the B port, so fluid goes out a single port to the cyl and then back into that port when you pull the handle back, holding it against the relief.

The lever trying to put fluid into the plugged work port will cause the relief valve to activate, however, fluid will flow out of the cyl through the work port.

You could however run a hose from the plugged work port to tank, so the flow will flow freely to the tank due to the load or bucket.

 

[VAFarmer6]

Here is my take on that valve.

If a DA valve is used with an SA cyl, some people plug the A port or the B port, so fluid goes out a single port to the cyl and then back into that port when you pull the handle back, holding it against the relief.

The return stroke will cause the relief valve to activate until the cyl is empty because that port is plugged.

You could however run a hose from the plugged work port to tank, so the flow will flow freely to the tank due to the load or bucket.

Finally found a hydraulic shop that was slow this winter and took the valve AND the cylinders over to them....they checked them all out and basically said they were not only shot, but never ever could have worked the way they did... they said I should use the cylinders for boat anchors and throw the valve away. So got on line and I bought a new 2 spool DA valve from Surplus Center and two new DA cylinders from Bailey..... not sure will ever put cylinder(s) on the bucket but got the dual spools just in case... Got everything on hooked up except the hose to the pump side of the valve....I put that hose in a bucket first and to pump out the old oil before I tried out the new setup .. fired up tractor and NOTHING was coming out of the line.... got to looking around and oil was gushing out of the valve port of the new valve that was labeled as P.... so on top of all the other apparent jury rigs on the orignal setup, the valve itself was in fact hooked up with the pump hose connected to the tank side of the valve and vice versa.... Cleaned up the mess.....switched the hoses around...put in the new oil and the "new" loader works like a champ.... so, have no idea what the "problem" was that made the SA stop working, but just about everything that could have been done wrong was done wrong!! Do appreciate all the time effort and consideration you all gave me.... in the mean time, I have become a self proclaimed expert on the Marvel Schebler TSX 811 carburetor if anyone needs any help with one of them!!! Now have one sweet running old Oliver 550 with a front end loader that works like a champ!!!! Thanks again guys.

 

[cropduster69]

Here is my take on that valve.

If a DA valve is used with an SA cyl, some people plug the A port or the B port, so fluid goes out a single port to the cyl and then back into that port when you pull the handle back, holding it against the relief.

The lever trying to put fluid into the plugged work port will cause the relief valve to activate, however, fluid will flow out of the cyl through the work port.

You could however run a hose from the plugged work port to tank, so the flow will flow freely to the tank due to the load or bucket.

Hey JJ. Here is some pics of the valve and the way it is plumbed now. There is now, no "external " tank, only using cylinder as reservoir. Yes, there was an external tank before, even though the cylinder is of the "self reservoir" type, but when external tank was in the system, would time after time, blow out the gasket of the piston end "end cap", so I bypassed the "external" tank, and now, no blowing out of the gasket. Before with external tank in system, gasket would blow when piston reached the end of it's travel. By the way, there are no "port" markings, so I have no idea which port would be A, B, etc. and thanks so much for your time.

 

[J_J]

Your center picture shows both work ports plugged, with two other hoses connected to something.

How is anything working as cyl need the A and B work ports to function.

A single action cyl needs one of the ports to work, or it can use two just so the relief doesn't go off.

Something is wrong with that picture.

 

[cropduster69]

the center pic is showing the valve mounted inverted. The two hoses, one comes from the PTO and the other goes to cylinder. I did take the "cylinder" hose from its side mounted location and revered locations on the "bottom" with the "brass plug". Operation of the bed was the same.

Here is the plumbing - large hose from "cylinder return"(external pipe into base of cylinder), then to PTO, out of PTO to valve, from valve to cylinder.
You are calling the two ports on what is now the bottom as A & B?

 

[J_J]

What I see is totally wrong, but if you made it work for you then so be it.

What I think you are doing is, when you raise the cyl, you engage the PTO pump, which sends fluid trough the valve to the base end of the cyl, and it raises, and when you shut off the PTO pump, the cyl descends by pushing fluid out, back to the tank.

Anyway, here is how a SA cyl is supposed to work.

The pump in an open center system and is always pumping, and the flow is through all valves IN port to the OUT port, to reservoir.

An SA cyl is connected to one of the work ports and the cyl is raised by pushing or pulling on the lever to direct fluid to to one of the work ports.

When you want to retract the cyl, you push or pull the lever and that directs fluid to the plugged port and the relief sends that fluid to tank. It also allows the fluid from the SA cyl to flow out the same port it is connected to, to tank.

 

[cropduster69]

Thanks and yes, but from the pics, can you tell me which is "in" ports and which are out? There are no "bossed" markings, only the logo of
Greson Hydraulics. If the valve were right side up, there are two ports on top and one each side.