1991 520-H transmission issue

[RPDeP 4]

Hi all.  Long time lurker.  First time poster.

 

My 520-H transmission has ceased to operate after changing a set of hydraulic hoses (purchased from Wheel Horse Parts and More) and replacing the lift valve o-rings.

 

Due to some leaking oil, I initially changed the two hydraulic lift hoses from lift valve to lift cylinder, the short ones.  All checked out and worked fine.

 

Then I rebuilt the hydraulic cylinder with new rings/seals from Wheel Horse Parts and More.  All worked fine.

 

Finally I decided to replace the two remaining hoses that run from lift valve to charge pump and lift valve to transmission filter, along with the 2 o-rings in the lift valve (used Harbor Freight nitrile o-rings 7/8" x 5/8" x 3/32" as measured best I could, in the lift valve).

 

Now I have no hydraulics after much time activating forward and reverse to overcome the air in the system.  I assume the charge pump is self-priming.  Though I did dump some oil into the charge pump from the top inlet port later in my efforts.   Only a slight spin of wheels when rear wheels are elevated.  No lift cylinder action at all.

 

I checked and rechecked all connections to ensure they were installed in the correct locations.

 

Could the lift valve o-rings be at issue?  Was there an untimely failure of the charge pump?

 

Thanks in advance for any suggestions,

 

-Rich

[JCM 9,328]

Maybe @wallfish John will chime in after work and lend some suggestions. Quite talented individual when it comes to hydraulics. And a heck of a guy.

[wallfish 17,078]

Well thanks Jim! Appreciate the pat on the back but hydro transmissions aren't my specialty. Adding hydraulics for loaders and back hoes is something I have experience with.

Still, replacing those hoses and O rings shouldn't stop operation. Unless they ended up going on backwards but that seems to be checked already. Changing them will consume quite a bit of fluid and air will definitely effect the operation. Make sure it's full of fluid/oil. You can usually hear the pump start pumping fluid after starting the engine. Make sure the belt is connected and spinning the pump. My 520-HC doesn't have a belt disengage lever but the 520H might. 

You can crack open the hose connections in the order of the flow direction from the pump to validate if fluid is coming out. Just enough to leak because high pressure fluid can be quite dangerous when peeing in a small steam.  

[RPDeP 4]

Thanks for the quick reply @wallfish.  Sump is full but it doesn't seem like the fluid is moving.   I'll have to recheck my connections and see if I can verify any fluid is moving in the system.

[Handy Don 12,436]

You do have the Eaton 11 manual, right? It's in the files on this site--search and ye shall find!

 

Specs call for max of ~700 psi. Two ways to hit that are:

- hold the control full up or full down after the cylinder is fully extended or retracted

- stall the cylinder with a load greater than it’s capacity

Either of these should trigger the relief valve (part of the control valve) to dump fluid directly back to the filter. That’s the “squeal” and it is normal.

Any other interruption of the flow is incorrect plumbing or a blockage or a failed part.

Because things are so tight around the hydraulics and with the steel lines, it is hard to get a gauge attached to the system while assuring continued flow without some significant disassembly.

 

The charge pump pulls from the transaxle sump via the large metal tube and yes, as long as it is “wet” with some residual oil in it it will pump but it is NOT technically self-priming. It drives the oil through the lift valve (or cylinder/relief valve) and then to the filter and back to the sump and at the same time directly into the motion pump--all under more or less pressure depending on the resistance in the circuit (load on the cylinder, cylinder fully extended or retracted but valve still full up or full down) or clogs in the filter. Blockages of an unmolested system are essentially non-existent. Once opened, bets are off. 

 

My first guesses would be:

- you’ve got a kinked hose or tube that is choking off the flow

- a dislodged o-ring or seal that is causing a blockage

- one of the check valves is stuck

Were you extemely careful to prevent any sort of debris or contamination from entering any of the tubes, hoses, valves? Kinks (bending a steel tube, for example)?

 

Be careful not to work this machine unless you can confirm good flow and pressure from the charge pump. Absent a good continuous supply of oil from the charge pump the motion pump/motor could go “dry”, heat up very quickly (a few tens of seconds quickly), and be ruined. And pay heed to @wallfish’s warning. 700psi is not like the 2-4,000 psi fluid on the big equipment, but it can still cut into skin in a thin stream.

Edited June 16, 2023 by Handy Don

[RPDeP 4]

Thanks Handy Don for your quick reply. 
 

Yes, I have been using the manual as reference. I kept the hoses capped and inspected ports for dirt when installing to avoid the introduction of contaminants the best I could. 

 

Your brilliant description will allow me to focus my efforts better on the most likely issues.  

 

Thanks again. 

[JoeM 7,874]

A quick check to see if oil is flowing would be to remove the spin on filter and crank it or start it up on idle and see if supply oil comes out of the filter housing ports. The one nice thing about the eaton 11 is all the oil is filtered going into the hydro. Plus who knows but the filter could be the problem. 

[squonk 41,291]

What filter is on it? 

 

 

[lynnmor 7,352]

Since the replacement hoses with their oversize fittings are difficult to work with, my thought is that you either have them reversed or the bottom one is sucking air.

[squonk 41,291]

Or it's air locked. Loosen the filter and see if you get flow cranking the engine 

[RPDeP 4]

Thanks everyone for the additional responses.

 

I have a lot of great suggestions to work with and investigate.

 

Using a Toro filter #79-5270.

 

Appears to be no flow with filter loosened while idling engine for a short time.

[Handy Don 12,436]

So with the filter loosened, there is no steady flow of oil coming out under pressure while the engine is running, correct?

 

My next step would be to loosen the nut on the JIC connector at the charge pump output (i.e. for the tube that leads down and forward to supply the lift control valve). 

Just a couple of turns, do NOT fully disconnect it, the pressure will force oil out of a loosened connection. (A working pump can move over a gallon of oil in 60 seconds so a disconnected tube would be a REAL mess.

Prepare for oil to ooze/stream/spurt/spray out of the connection and then crank the engine and be ready to shut it down pronto. 

 

If NO oil squirts out, you have found the source of the problem. The pump.

If oil DOES squirt out, then the pump is probably working and the problem is something stopping the oil from getting through the control valve and back to the filter. One simple plumbing switch could be the problem--if the tube from the pump is going to one of the cylinder ports on the control valve (known as A and B ) instead of the IN port. IN and OUT are on the side of the valve facing the front of the tractor. The A and B ports are on the bottom, facing downward.

 

BTW, the standard WH control valve has what’s called a “Tandem” center. When the lever is in the middle position, the oil goes directly from input to output and the cylinder lines are closed off to “lock" the cylinder in position. A feature of the valve is an integrated pressure relief valve. It does NOT have “power beyond” capability.

 

 

Edited June 17, 2023 by Handy Don

[RPDeP 4]

Ok.  Oil did come out of the charge pump output.  And it was frothy.  That was my clue it was churning on the same oil and there was a blockage.

 

Immediately disassembled (again) the lift valve and went for the charge pump 'out' to lift valve 'in' hose to check for obstruction.

 

It is completely obstructed.  I also immediately checked the lift valve output hose for obstructions.  It was fine. 

 

So I put the old hose back on and everything was fine. 

 

This all started because I was experiencing slight transmission fluid leakage on the lift cylinder and couldn't pin point the source.  

 

So I still have some leakage coming from somewhere.

 

I plan on cutting into the blocked hose to see what the issue is.  

 

Not sure if I introduced the hose blockage or if it was built like that.

 

A big thank you to all involved, especially Handy Don.

 

And I learned a lot about 520-H hydraulics.

[Handy Don 12,436]

1 hour ago, RPDeP said:

And I learned a lot about 520-H hydraulics.

Glad you are on the path to a solution. 

Let us know what caused the blockage!

Fingers crossed that you have no damage to the motion pump/motor while that blockage was happening. Is that a steel tube or a soft hose?

[lynnmor 7,352]

Later models used some steel lines. I suppose some of your problems could be eliminated if you could fit those.

[Handy Don 12,436]

58 minutes ago, lynnmor said:

Later models used some steel lines. I suppose some of your problems could be eliminated if you could fit those.

Only different problems, @lynnmor!

 

I just finished some work on a 520 chassis and had to change some hydro lines (rust and other reasons). I used modern copper-nickel brake line. Thin-wall steel tubing (as originally used) is not so easy to come by and the Cu-Ni stuff won’t rust or corrode and is not as hard to work. Cu-Ni doesn’t have the maximum pressure rating of the steel, but its burst strength for ⅜” tube of ~4,000 psi well exceeds the 700 psi for the Eaton 1100 charge pump so I’m not worried. It does need solid bracing for runs longer than 18”, per the spec.

 

BTW, as a hard line, that run from the charge pump output to the control valve input has some tricky bends and cannot be removed (or replaced) in one piece without a LOT of tractor disassembly. I’d bet that during manufacture, it was put in place even before the rock shaft and transaxle.

 

I’ll have this tractor at the show so you can stop by and see what I did.

Edited June 17, 2023 by Handy Don

[RPDeP 4]

It is a soft hose.  

 

I cut grass (1.5 acres) today using a 60 inch deck and no issues with the lift or drive wheels.

[RPDeP 4]

I cut the right angle connectors off the ends of the hose and one of them is blocked.

 

I can't see light or push air through it.  The hose is fine, as is the other connector.

 

The blockage is in the 90 degree elbow and not in the crimped area.

 

I may try to cut apart the elbow to really identify the issue.  

[Handy Don 12,436]

11 minutes ago, RPDeP said:

I cut the right angle connectors off the ends of the hose and one of them is blocked.

 

I can't see light or push air through it.  The hose is fine, as is the other connector.

 

The blockage is in the 90 degree elbow and not in the crimped area.

 

I may try to cut apart the elbow to really identify the issue.  

Pictures, please!

[Bill D 1,932]

7 hours ago, Handy Don said:

Pictures, please!

Yes, please post pictures.  I'm sure Wheel Horse Parts & More will replace your defective hose.

[RPDeP 4]

Here are the pictures of the cut up right angle hose connector.

 

Edited June 20, 2023 by RPDeP

[RPDeP 4]

An these final two tell the story.

 

 

Edited June 20, 2023 by RPDeP

[Handy Don 12,436]

Wow. So a manufacturing defect that the oil passage wasn’t fully drilled out. 

Like you, this possibility would have been WAY down on my list.

 

[RPDeP 4]

Tells me the connector manufacturer doesn't test/check the connector nor the hose manufacturer the completed hose. 

[Handy Don 12,436]

31 minutes ago, RPDeP said:

Tells me the connector manufacturer doesn't test/check the connector nor the hose manufacturer the completed hose. 

Yep. Kinda makes you want to grab someone and shake them.....but better not.