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JD 410 Hydraulics

telwood

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Mar 20, 2013
Messages
123
Location
GA
I've got a JD410 backhoe about 1975 model.
I've had hydraulic problems but after adjusting pump got everything working good...until recently. Went to use the machine and all the hydraulics are extremely slow (backhoe and loader equally). Since I had raised the pump PSI last year to the book PSI of about 1600 psi it ran better than ever so I figured the filters and screen were dirty with the added pressure. Changed both filters and cleaned the screen but no change.

The pressure is holding at about 1800 PSI but when I engage the loader or backhoe hydraulics it falls to about 600 until I let off.

Any thoughts what is causing this?

Thanks,
Tom
 

Delmer

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Jan 3, 2013
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The charge pressure to the hydraulic pump isn't keeping up. You can probably put a gauge on the low pressure side of the pump and verify this. Does this hydraulic pump have the charge pump as part of the radial piston pump, or does it get pressure fed from the transmission?

Was there anything in the filters or screen? Take a section of the filter about 3"x3" and put it in a vice and squeeze the oil out, then look for metal or whatever in the bottom of the folds. Or rinse the filter off with solvent and drain off the solvent, rinse again with solvent and see what's in the bottom of your container, glass or a white plastic container works best for visibility.
 

lantraxco

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Jan 1, 2009
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Elsewhen
Transmission pump feeds the hydraulic pump, but also the return oil gets filtered and backfills the inlet side of the piston pump... the tranny pump only provides about half of the maximum flow at best. Check the hydraulic return filter, there's a charge relief spool valve that dumps excess oil back to the transmission case, if it sticks open you lose charge pressure.
 

telwood

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Joined
Mar 20, 2013
Messages
123
Location
GA
Transmission pump feeds the hydraulic pump, but also the return oil gets filtered and backfills the inlet side of the piston pump... the tranny pump only provides about half of the maximum flow at best. Check the hydraulic return filter, there's a charge relief spool valve that dumps excess oil back to the transmission case, if it sticks open you lose charge pressure.

Does the below diagram show the relief spool valve you refer to?

Thanks,
Tom

upload_2017-7-31_19-35-24.png
 

telwood

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Mar 20, 2013
Messages
123
Location
GA
Yup, #14 I believe.
Seems I need to get back in there again. Months ago I removed it and tried to put the washer in the groove on part 14 which was not installed and couldn't get the part back in the hole with the new washer. The parts all seemed fine and I reinstalled without the washer and seems to have worked fine. Maybe the washer part came wrong...not sure but will check that first.

Thanks,
Tom
 

telwood

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Joined
Mar 20, 2013
Messages
123
Location
GA
Better late than never but was building my shop. So I checked the above parts and founding nothing there seemed wrong.

I got the pressure on the pump set at about 1600 and as soon as I engage either the loader or backhoe controls it drops to nearly nothing and the operation is super slow....like not useable.

Any other reasons as it isn't releasing charge at the spool in the filter (see above)?
 

telwood

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Joined
Mar 20, 2013
Messages
123
Location
GA
upload_2017-8-27_19-26-27.png
I did notice as I got back into the control valve the spool #5 above seems to float freely in the housing. I can't seem to take out that part (#5) as it doesn't come out the left or right and of the housing. I opened the left side (bolt #6) and removed the parts down to the #4 fitting which are inside the spool and the spool moves in the housing. Does that spool come out on this end? When I had the housing off last year it didn't come out either end but moved freely even when the spring was in.
 

telwood

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Mar 20, 2013
Messages
123
Location
GA
Yep, wasn't born in there and I got it out. Those parts were all fine and am planning to have someone come over tomorrow with gauges to track the pressures. I've got 2000psi standby and when I activate either the loader or backhoe it drops to 500psi. and the equipment runs at snails speed.

One thing I noticed today was the brakes are gone....free motion when compressing the brake pedal with absolutely no engagement of anything.
 

Delmer

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Jan 3, 2013
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I jumped to the conclusion that your charge pressure wasn't keeping up. But check that first. If the charge pressure is fine, then the first place to check might be the pressure control valve, or whatever JD calls it on the main hydraulic pump that you adjusted the pressure on.
 

telwood

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Joined
Mar 20, 2013
Messages
123
Location
GA
Ok, took the destroke portion off the hydraulic pump and took it apart. The special washer (O) was on the wrong side of the spring but everything else looked good. My unit has a bolt on the top rather than that adjustment wing but has been that way for years. Also I don't have the electric solenoid unit (K) on the side.

The only other thing I noticed was how tight the pin (B) is but doesn't appear to move in the housing.

I went ahead and ordered new seals and spring incase it is compressed due to age. Anything else to look for? I was thinking maybe the spring was cocked since the washer was on the wrong side but nothing else obviously wrong I can tell.

410 trac2 001.jpg
 

telwood

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Joined
Mar 20, 2013
Messages
123
Location
GA
This equipment is driving me crazy now. Removed and changed some parts out on the above stroke control valve, re-installed it yesterday and am getting nothing from the pump. After leaving off the stroke control module for a week awaiting parts quite a puddle....do I have to prime the pump? I checked some lines to make sure the oil cooler line weren't clogged, and lines were feeding the pump. I'm not even sure what else to check.
 

Delmer

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Jan 3, 2013
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It's time to get a service manual. It will have a step by step diagnostics that will find the problem. Jumping around is fine if you have a couple things that are the likely causes, but once you've eliminated the most likely causes, or failed to identify the issues, then it's time to step back, study the whole system until you understand it, and follow the manual.

As long as the oil level is OK, then you don't have to prime the pump.
 

telwood

Well-Known Member
Joined
Mar 20, 2013
Messages
123
Location
GA
It's time to get a service manual. It will have a step by step diagnostics that will find the problem. Jumping around is fine if you have a couple things that are the likely causes, but once you've eliminated the most likely causes, or failed to identify the issues, then it's time to step back, study the whole system until you understand it, and follow the manual.

As long as the oil level is OK, then you don't have to prime the pump.

Yep, I'm at that point. I think I'll contact the mobile service folks and let them figure it out. I've got the manual and the test equipment acquisition makes no sense. I built the shop to bring in my 455G and do a few things on it but now am backed up.

Thanks,
Tom
 
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