JD 4020 intermittent hydraulic chatter

Hello,

We have a 4020 with intermittent hydraulic chatter. I have just started working on it but the problem has been worked by a few people first.

The tractor is a late model with the side console and syncro-range transmission. It is used to operate a JD 158 loader from time to time. We do not have the loader installed now though.

When it is acting up I hear the pump chattering but also hear chatter near the steering wheel. The front pump was already replaced and pressure adjusted. The new pump was actually a rebuilt one, but with a new housing. The control valves were all rebuilt. The work was done by a professional, not by us. It should theoretically be good, and no longer part of the problem.

I checked the pressure from the transmission pump. It maxed out at 140 PSI, I don't have a flow meter or I would have checked the flow. The manual said to remove the transmission filter cover and filter, crank the engine, generous amounts of fluid should flow out of the filter housing. I got nothing with it cranking, but when I start the engine it pours fluid out like it should. I have not cleaned the sump screen yet. I wasn't sure if not flowing when cranking was a problem or not so I checked the pressure at the priority valve, just after the front pump. It sits at 2250 when the tractor is running at idle, just like it should. As I am operating things, even the front loader, the pressure stays relatively constant. As long as I keep the RPMs around 1900. When the tractor starts it's chatter the pressure drops down to around 500 PSI. It'll start to chatter with the clutch in or out but it does it more when the clutch is depressed. To stop the chatter I can wait it out or sometimes just give it more RPM's

I have already found that the brake valve is leaking. For troubleshooting I have taken that out of the system. Removing the brake valve made the tractor run much much better. It does the chatter much less, this makes me think I need to hunt for more leaks.

Where should I head next? Does it seem like there may be a problem with the trans pump? 140 PSI seems plenty, doesn't it? It just doesn't flow when cranking. Is it worth buying a flow meter for testing? I was quoted $160 for one I can add to my manifold. That's a lot for just the one test.

Any pointers would be greatly appreciated.

Thanks

PrindelCreek
IIRC 140 psi for trans pump is a little low and I think oil should flow from trans pump at cranking speed. Possibly internal hyd leak(rockshaft for a start),leaking stroke control valve or faulty outlet vale in main pump to name a few places to check. Flow meters are very helpful in diagnosing closed-center hyd problems.

i think you need to replace trans pump but check the screen first your pump up front is running short of oil

The PSI from the trans-pump has nothing to do with your main pump working, or not. It certainly will affect your trans if you have a Power Shift and not a SynchroRange.

Main thing is that oil is being delivered to the front pump. If there is flow, even 1 PSI will work fine. But, obvioulsy, a very low PSI reading indicates either a massive leak somewhere, or a trans pump that cannot make any flow.

A simple "bucket" test works fine. Just see how much oil the trans pump can put into a bucket at cranking or idle speed. We rarely used a flow rater in our Deere shop for trans-pump diagnosis since it was not worth the set-up time.

Start with the most obvious thing first. The transmission-pump pickup screen at the the bottom of the trans.

These other guys are most likley correct. The noise you hear is called cavitation. This is a differential pressure that occurs in the lines. It does cause damage to the front pump if it occurs for a long enough period of time. It also causes line to vibrate which causes expidited wear and leaks.

As the others said... Check your screen under that round plug on the LH side of the trans case then do a filter change. I'm guessing that your rear pump is worn after all these years of use, but you might get lucky with a screen cleaning and filter change?

If you do have to replace your rear pump I know that Deere offers a higher volume pump as a replacement for some of the older tractors. They may or may not offer one for a 4020, but you may want to check into it if you have to R and R the pump.

Well I'll have to change the screen and do my best to find internal leaks. If I do have to replace the trans pump is there any way to do it without tearing the tractor in half? No super secret access ports?

Thanks again

There does not appear to be a trans pump upgrade for the 4020 unlike the 4430 etc.
As long as the trans pump isn't scored from debris. And if there is no phantom high pressure side leak.
It's either restriction on the trans pump intake side. Or one of the multitude of the transmission pressure control/relief/diversion valves.

So many things can contribute to a chattering noise in your front pump. Does the chattering go away if you use a hydraulic function ie steering, rockshaft, scv? If so, check your hydraulic pump coupler. Does all of your hydraulic functions still work when this chattering occurs or do you lose any or all? On the low pressure side or charge circuit your filter and sump screen are the easiest to check but remember to drain your oil before removing the sump screen ro you will have all your oil flowing out right at you. Before doing a transmission pump flow test, try doing a few checks on the high pressure side. You can take several circuits out one at a time to check for a high pressure leak that is demanding more oil than the transmission pump can deliver. You can block off the brake valve which I understand you already did, you can cap off the rockshaft and scvs together. The lines connects to the rockshaft housing under the operators platform. You can also cap off the line to the steering valve which may be of intrest since you indicate that there is a chattering under the dash. If you cap off the steering and your chattering stops, don't assume that the probelm is in the steering valve. The pto valve also gets it's feed from the same line that feeds the steering. You could have a leak in the pto valve or brake. Another easy test is before you cap off the steering valve or any other for that matter, engage the pto and see if your chattering goes away. If it does, you have a leak in the pto brake. In addition, keep in mind that the presure control valve is under the cowling on the right side and a broken spring or sticking valve could cause a chattering noise. Does this chattering occur at first start up and fine after? If this is the case, your transmission pump could be losing it's prime. There is a check valve in the transmission case that sticks. The remedy for that is to install a check valve in the elbow fitting to the line that feeds the main pump. I have also seen the filter relief valve be held partially open from a small amount of debris. This valve is located in the housing back by the plug where the sump screen is located. Good luck and if you are in need of further assistance, please feel free to e-mail or repost.

The chatter doesn't toggle by using anything in particular on the tractor, at least nothing that I have found. It goes away on its own or by increasing the RPM's a bit.

When it is chattering we loose pretty much all hydraulic function. It has about 500 PSI which isn't enough to even steer.

I am definitely going to cap off some more stuff and see what I can eliminate. The steering valve is definitely on my list! I read a test that said when you shut down the tractor it should maintain pressure for about 5 minutes as long as nothing is operated, is that correct or did I misunderstand. That seems like a very helpful test.

Can you think of any tests to test the pressure control valve? Is that the same as the priority valve? I read a test of the priority valve in the I & T manual

The chatter doesn't go away as it gets warmed up. It comes and goes as it pleases, maybe even a little more after warming up.

One more question, the 140 PSI that I am seeing at the trans pump, would you say this is low pressure and worth investigating? If I do need to replace the trans pump is there an easy way to do it or do I really need to split the tractor in half. If so we will likely have someone else do it for us.

Thank you for the detailed reply. I'll have to print it out and take to the shop next time i go.

PrindelCreek
As I previously stated along with other posters
" Some diagnosing and screen cleaning is needed before parts are changed".

The trans pump is bolted to rear of top shaft on the trans. It can be changed by removing rockshaft housing(3 pt lift cover).

When I stated 140 psi was a little low I didn't mean to imply that that was the problem with the hyd chatter or that a Flow meter was necessary to check trans pump flow. I meant that a flow meter was nice to check main hyd closed-center pump for output in gpm's.

i just had a 4320 in my shop with bad hy. sota same problem as you discribe. first thing i did was check transmission pump bucket check works good. if you have a idea what it should pump per minite on 4320 it is i belive 6to p gal permimite the late 30 serie were like 12gal per minite. it had little flow so removed 3pt and checked pump it was scares bad gears so though problem solved replaced pump. as useal thies closed centre systems never are simple. replace pump installed top cover. checked flow was way better. but still had chatter so went to check stroke control in process the sterring line going under the steerin box broke so off come fuel tank resivor rad. finily get to where i can replace line. you know this ol tractor was clean lol; replaced line other line to steering unit was also had a creck in it fixed it now to check hy, left off rad. fixed a small tank to run tractor still no hy. to speak of. i have a good used pump off a 4430 so install it know is good still chatter. take it off put other pump back on. ok this tractor has a loader on it power is drived fron pressure line going to pressure control valve. i know not the way it should be but that how it is, now think block off line to pressure control valve a penny works good in this type fitting tighten up line tell it forms on to fitting making a quick block, loader return goes back into hy filter housing. so ok if pump is good and transmission pump is pumping oil this should tell well still have chatter so i know now is not a leaking 3pt valve or remote leak steering leak as only thing in system is the loader.good pump new transmission pump. i an to point i want to shoot this tractor. so back to basic sometime i have good flow sometime i dont from transmission . so i take off pressure control valve housing cloes to filter. this has surage valve oil filter by pass and a couple other valve in it,. inspect it seem ok. the surage valve spring seems to be a slight bit weak so throw a couple shims in to give it some incresed tensenion. then i stretch the spring behind one of the other valves. put it all back together. cross finger start tractor and dam if i dont have hy like a new machine. now the main problem was transmission pump but i think what realy solved the problem was the surge control valve being weak ;; so you might get some new spring and install them in that control valve thank there are 4 springs i would have use new if the dealer had them on hand. but he didn;t and i want to see if that was problem before ordering.like i said before the hy system on thies ol tractor can be one big head ack. but thy are fix able you can have all the fancy tool tedt gage and all and still have trouble fixing them. is my feeling that the chatter in thies system is probly from lack of oil from transmission pump. if your oil is heating the problem is most likely in 3pt or remotes or the steering system.

The pressure control valve is the same as the priority valve. It's job is to maintain approximately 1800-1900 psi for your priority functions such as steering, brakes, diff lock. The only test for that that I know is to check your high pressure while raising the rockshaft or using the scv. Your high pressure should drop to the priority pressure. If it doesn't, there could be something wrong with the pressure control valve, but also a problem further upstream. Does the transmission pump pressure maintain 140 psi when the chattering occurs? Actually the 140 psi, which by the way is about where the transmission pump relief is set, should only be if there is no demand for oil. Usually when there is a demand for oil, the pressure will be very low. Usually, the stroke control valve will not cause a chattering noise, btu I would not rule that out. There is an inlet screen in the main pump that could be restricted that would allow the trans pump pressure to stay at relief and would cause the chattering due to starving of oil. The transmission pump can be accessed by removing the rockshaft housing. It is driven off the basckside of the transmission top shaft. Good Luck!

JDTECH,[/quote]It's job is to maintain approximately 1800-1900 psi for your priority functions such as steering, brakes, diff lock.

Would you please explain your statements?

The way I remembered the priority valve function is this way. If stand-by pressure drops below the set pressure it closes so to have emergency pressure only for steering & brakes. I think if stand-by pressure stays above the set pressure during raising rockshaft priority valve will not close. If first statement is correct then how could one check stand-by pressure at SCV of which I've done?

How can priority valve provide oil for "diff lock" when it is located to the rear of priority valve???????
Thanks,Jim