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1978 JD 410, trans oil foaming

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Djdnl

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Discussion starter · #1 · (Edited)
Hi, ive posted about this machine before, and I replaced the backhoe control valve assembly(used) and that fixed the fluid getting hot leaking past the spool valves. Thanks to all who helped.
It was working fine, then lost pressure. I have traced the problem to air/ foam in the line to the pressure pump, from the trans pump. If i remove the test port at the pressure pump, air bubbles are present, ive even run it with a hose from the port into a bucket, and the fluid is full of air.
With the dipstick removed i can hear the pump whining/cavitating in the transmission. I can see the bubbles circulating around the reservoir.
Trans pump seal? That is what I think. Has anyone had this problem?

Thanks for looking. Dave

By the way, filters are new and trans screen is clean
 
Discussion starter · #5 ·
So what your saying is even though the fluid isnt dripping when the machine is off, the pump has enough suction to pull air in? Maybe the hose between the hydraulic filter and sump? Dave
 
#6 ·
Are OEM filters or after market . Did this problem start after cleaning screen and filter change. Was the machine idlking for 15 minutes before using the hydraulics ? Have you tried cracking a few lines to get air out . No debri in tank causing a line to get plugged off ? Screen installed properly a check fttings ? Yoiu could spray wd 40 or oil and see if itks getting pulled in anywhere . Raraly a hose might be bad internally causing somethinh like this , If you have your old filters cut the top off abnd take them apart and see if. There is anything trapped to give you a clue . Brass not good .Rubber O rings or hose . Might be worth getting someone in to do hydro tests to find the problem if the above is checked out. First ,
 
Discussion starter · #7 ·
Napa filters. Problem started as I was using the machine
No,I did not wait 15 minutes. As soon as i start it, I can see bubbles in the reservoir thru the dipstick. I let is sit for 3 hrs, till there wasnt any more bubbles in the oil, then started it, and within 5 seconds I could see the fluid bubbling.
Im going to pull screen out tonight, and replace that short hose and hose clamps betwwen the filter housing and screen.
Dave
 
#10 · (Edited)
It won't , it may slow the flow down or go to fast causing the air to mix in at the pump . Nappa filter might not be the right micron filter or type for the machine . If you didn't spefically match specs to nappa filter then it's probably not the right one . That filter may screw on but might not have pressure relief or right micron filtering system . May not be a specific to machine filter but a filter that can be used in many other machines . 15 minutes at idle . Always use Oem filters for hydro's unless Nappa can match the SPEC'S of your filtering system . Not by crossing over # !!!!!!!!!!!!!!!!!Plus when trouble shooting you can rule the filter out with the OEM .
 
#11 ·
BobP said:
That filter may screw on but might not have pressure relief or right micron filtering system . May not be a specific to machine filter but a filter that can be used in many other machines .
Click to expand...
The hyd filter on a JD 410 has no relief valves in it nor is it a screw on type. It is possible that the suction tube is leaking on the trans pump.
 
#13 ·
Would it be possible, seeing that you have replaced parts, fittings, that you have air trapped everywhere in the system, which may need time/flow through........and a subsequent recheck of the oil level, which is probably low?
 
#14 ·
Djdnl said:
TX Jim, Is the suction tube you are refering to the one between the filter and sump. Or could it be leaking inside the trans?
Click to expand...
I have a lot more experience with JD closed-center hyd systems on ag tractors than the ind models. But if the suction line on the trans pump is leaking it can cause the hyd oil to be foamy. Some brands of hyd oil do not mix with other brands of of oil and that can cause foaming(air in the oil).
 
Discussion starter · #16 ·

Replaced the hose from the filter to sump. Checked the screen, it was clear. Removed the trans filter relief valve. It looked ok/spring not broken/it moved freely.
Refilled fluid, and it seems to be working. fluid still gets air in it, but not as much. Local JD tech thinks there is a problem with the pickup tube in side the trans. Ill have to wait till saturday to go dig with it.
Dave
 
Discussion starter · #18 ·
So does the strainer connect to #22, because that would make sense that its working better after removing and putting it back in.
Can I get to that tube by removing the top cover off of the trans?
Thx Jim.

Dave
 
#19 ·
My experience is with agriculture not industrial tractors BUT I'm fairly confident that the screen is way farther towards the rear of trans case than the trans pump. I wish I had an industrial technical manual so I could look at the oil schematics.
 
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Tx Jim
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