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| Bought this 4020 syncro year ago in sad shape had to rework injection system, starter, and various other things just to get her running. Been using it for light pto work ie mower auger etc. This fall hooked it up to a shaver hyd postdriver and noticed when we raise hyd ram on driver hyd hose vibrates and hyd pump seems to cavitate . Check/ CHANGED fluid/ level, changed hyd filter cleaned sump screen, checked pressure at remote 2250, still the same. I also cranked tractor over with filter out seemed to have flow from transmission pump but unsure if it is enough. Have not taken stoke control valve out yet, but that may be the next thing I try, just seems to me that main pump is short on fluid or something is wrong with it. I keep leaning towards the transmission pump not providing enough fluid to main pump. but could be way off. TIA STAN |
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west central illinois | Have you destroked the front pump yet? |
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just a tish NE of central ND | It seems to me that there is a oil screen in the front pump somewhere under a plug. I'm not sure which plug though. I believe it may be under one of the piston plugs. Should be able to access from under the tractor. Not sure though as tis been a long long while since I have messed with a pump like those.
Maybe someone else can chime in. |
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Virginia | Check the valve on your Shaver driver. You need one that works on a closed center system. |
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| +1. To check your driver valve remove return hose to tractor and hold in a bucket. Start tractor and open supply to driver. If oil flows through driver valve in neutral the valve will have to be converted for use with the 4020 closed center system. Hope this helps. |
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western iowa | Are you on the tractor with your foot depressing the clutch pedal when this is happening? 4020's only push oil forward to the main hydraulic pump when you have the clutch out. The reservoir/cooler is supposed to keep some extra supply when you have the clutch pedal down but, using lots of flow you will run out. It's like trying to raise a barge wagon hoist with the clutch in.......you will run out of oil. Just a thought if you are unfamiliar with 4020's. The newer tractors don't have this issue. The front pump is fed all the time. |
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| I do have closed center valve on post driver have not destroked pump |
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Pontiac, IL. | Plus 1 on what classic 4010 says. |
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Between Omaha and Des Moines, 7 miles South of I80 | That's a good point. Shaver post driver on Dad's 4020, happens to be power shift, but when driving post = tractor in park and rpms set to 1500 rpm. Now, the older 3010, is syncro tranny, and it does run out of hyd fluid, for loader, WHEN you constantly have your foot on the clutch, too long. |
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| Also have had clutch out when operating remote |
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| You still need to check your driver valve out. Often on the auxiliary valves the packing on the closed center conversion plug will be bad or missing and will cause the described problem. Common problem on loaders. |
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| Shine a light into the filler tube while it's running to see if you notice any oil spraying around in the sump. There is a cover plate on the underside of the rockshaft. It has an o-ring that can blow out,our the cover itself can Crack. I had the same problem with a 4020, and this cover was cracked. |
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Fruita CO | Where are you returning the oil from the driver valve? It has to be run back into the remote, or else into a ported filter cover or the rockshaft return line. Can't just dump it back into sump.
Destroking the pump won't help or tell you anything if the pressure is 2250-main pump is OK. |
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Faunsdale, AL | I think it has to dump back to the sump to get the driver weight to drop hard enough. Ours had about 1.5" return hose connected to the trans filler of the 4020 with a pipe union.
I think I would check sump screen in bottom of transmission as well as sources of high pressure leaks. The closed center conversion plug leaking sounds likely though. I have one doing that on an old loader valve we put on a log splitter. Should pull it out and inspect. |
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Between Omaha and Des Moines, 7 miles South of I80 | Yes, the return oil must dump quickly. Dad's 4020 with Shaver post driver comes either 1 or 1.5" return hose and goes into a welded adapter, right into the tranny oil filler hole, under seat. Edit: Here's an old picture, I drew for a previous post: 
Here's a photo of how small diameter of hydraulic cylinder, on a Shaver post driver = doesn't need that much volume. 
Edited by 4WD 12/28/2014 08:33
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| Returning the oil to the sump guarantees a problem if you want more than a few gpm. The charge pump in the transmission has a lot less flow than the front pump can supply. This application is not suited for the 4020 hydraulic system. Returning to the oil filter cover or through the remotes does put a couple hundred PSI, the pressure from the charge pump, on the back side of a cylinder. A single acting cylinder won't close with the engine running without more external force on it than I can do by hand.
I have updated the service bulletins on my web page about loss with the clutch pedal pushed in with some on side console tractors too. www,geraldj.netowrkiowa.com/4020si.htm
Gerald J. |
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| There is a test in the I&T manual and the shop manual for flow and pressure from the charge pump for preside console 4020. that flow is less than the flow of the main pump. They expect return flow from loads to be to the front reservoir/cooler, not the sump.
Gerald J. |
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Virginia | + 1. We've returned the oil into tranny oil fill opening with 2 different Shaver drivers and 3 different JD tractors without any problems. Been working this way for probably 25 to 30 years. |
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| Checked and made sure closed center plug was in shaver postdriver valve, driver was purchased new and used on another jd tractor. I have the return line from driver dumping into the back of transmission case. driver cant have resistance to flow on the return. Going to hook 4020 up to some other plow with hyd ram and see if I have same hyd chatter. Thanks for all input keep yall posted on outcome. |
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| Later JD tractors were rated to return hydraulic motor flow to the sump, they must have had a much bigger charge pump than the preside console 4020.
Gerald J. |
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Fruita CO | well then, there's the problem... |
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Between Omaha and Des Moines, 7 miles South of I80 | ronm; Are you saying, that a big hose dumping into the sump; Is the problem? {Because Dad's old 1964 4020, doesn't have any problems for 30 years, running a Shaver post driver plumbed this way, and neither does HT67, per his post} Now, if something is wrong, inside the post driver's control valve, and constantly "dumping oil"; then yes, that would overwhelm the hydraulic system for the amount of flow. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Rereading the original post, we are assuming that this comment is accurate: "This fall hooked it up to a shaver hyd postdriver and noticed when we raise hyd ram on driver hyd hose vibrates and hyd pump seems to cavitate " Maybe we are putting too much, into this comment. Does the post driver still operate? Does the post driver's ram go up smoothly? Does the post driver's hyd. ram stay in the "UP" position when control valve lever is released? How about, if tractor is shut off? Does it bleed down? Does the post driver feel bouncy, like air is in the hyd. oil? Have you tried a different hyd. remote (at rear of tractor)? Have you tried and changed the hyd. tip, on that hose, for post driver?
Edited by 4WD 12/28/2014 12:23
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Faunsdale, AL | Ron, isn't there an oil cooler relief valve in the trans filter housing that can bypass oil back to the sump if it's defective?
I suppose the front pump could be on its last legs with several cylinders not pumping. This might show up when there is a significant flow demand and be felt better with your hand on the handle of the driver valve vs the levers on the dash controlling the SCV's.
The thing working on another John Deere tractor could mean it has an open center valve in it. Lots of the newer tractors are open center. The old loader valve on our log splitter is or was a closed center valve, but it is behaving like an open center valve now. Lots of chattering even though it does work the splitter when it's on a 4320, but works great on the 5055.
Edited by ccjersey 12/28/2014 16:30
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Fruita CO | All I'm saying is that particular tractor probably has an issue that's affecting the capacity...a big one-way cylinder dumping back to sump isn't exactly ideal, but if it worked on yours, it must be possible. theoretically, doesn't sound good. As far as i know, I've never been in the same vicinity with a shaver post driver, so first hand? No...
Oops-I had this ready to post about 4 hr. ago, then the game started... |
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Fruita CO | Yes, cooler relief could stick open & bypass oil.
some of those valves have an o-ring or a flat ring in the closed-center plug that will blow & bypass... |
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JOHN DEERE 4020 HYDRAULICS
