4720 steering is jerky

[qstott]

I’ve searched and expected to find some answers, but no luck. My JD 4720 cab tractor is a 2008 and now has about 1350 hours. The past few times while using the rear finish mower, I could feel a little jerking at times in the steering. At first it was just occasionally, bit seems to be getting worse. Today I used it for about two hours and it got progressively worse. It was a hot day, around 91 degrees. The a/c was cooling fine and the gauge didn’t show hot. If I turned slowly it didn’t do it as badly, but quick sharp turns was much worse. I think I know what i need to do, but I’m just seeking advice.

 

[LouNY]

I am assuming that you have checked the level of hydraulic fluid and the filters have been changed.
Does your tractor have a dual pump setup with one pump for the steering and a second pump for the remotes and 3 point.
Looking at the specs it appears to have a 5.1 gpm pump for the steering.
Have you checked the pressure of the steering circuit or the flow.
When that occurs with the steering it is normally an interuption of the hydraulic flow to the steering motor.

 

[arlen4720]

I’ve searched and expected to find some answers, but no luck. My JD 4720 cab tractor is a 2008 and now has about 1350 hours. The past few times while using the rear finish mower, I could feel a little jerking at times in the steering. At first it was just occasionally, bit seems to be getting worse. Today I used it for about two hours and it got progressively worse. It was a hot day, around 91 degrees. The a/c was cooling fine and the gauge didn’t show hot. If I turned slowly it didn’t do it as badly, but quick sharp turns was much worse. I think I know what i need to do, but I’m just seeking advice.

There is a sintered metal filter on the pressure side of the power steering circuit. It is on the left side. It often gets overlooked during maintenance. Have a look at that. The operator manual has more info.
Just take it out and clean it up.

 

[qstott]

The owners manual shows an inline hydraulic filter that has a direction of flow arrow on it. Is that the steering pressure side filter? They don’t show a specific steering circuit filter. The fluid level is fine. Thanks!

 

[arlen4720]

The owners manual shows an inline hydraulic filter that has a direction of flow arrow on it. Is that the steering pressure side filter? They don’t show a specific steering circuit filter. The fluid level is fine. Thanks!

Yes, that's the one. I believe the fluid flows from the pump, to the steering valve, then through the oil cooler, then through that filter, then it goes to the eHydro for lube/charge pressure.
If you've never cleaned it, you are certainly due at 1350 hours. I usually do mine every other fluid change or so.
You just take it out, and clean it with some brake parts cleaner. There have been a few cases like yours over the years, and that filter was the culprit. No guarantees though

 

[qstott]

So, if I take this apart, I’m assuming fluid will pour out. Is there a way to get around that? Btw, I was searching for a technical manual as was flabbergasted that one from Deere as $511.00. I found one on ebay in printed form for a little less than $200 and ordered it. I just didn’t trust the $26 one from Russia I could download.

 

[beenthere]

Is this the inline filter you are referring to here?
key # 16.

 

[qstott]

That’s the one!

 

[arlen4720]

So, if I take this apart, I’m assuming fluid will pour out. Is there a way to get around that? Btw, I was searching for a technical manual as was flabbergasted that one from Deere as $511.00. I found one on ebay in printed form for a little less than $200 and ordered it. I just didn’t trust the $26 one from Russia I could download.

you won't lose much fluid, maybe an ounce or two. Once it's off, the filter body comes apart. I might of been able to help you out on the tech manual

 

[qstott]

Thanks!

 

[qstott]

I didn’t have a chance to run the tractor long enough to really get it hot today. But, I’m sure I have improvement or maybe even complete success. I removed the screen from the filter housing and it didn’t have any gunk in it that I could see. However, the screen appeared to be sucked flat and collapsed. I opened it up carefully with a small screwdriver and punch. Cleaned everything and put it back together. The few minutes I was able to run it, there was no more jerkiness. The proof will come next time I give it a good workout. Thanks for the helpful tips!

 

[arlen4720]

I didn’t have a chance to run the tractor long enough to really get it hot today. But, I’m sure I have improvement or maybe even complete success. I removed the screen from the filter housing and it didn’t have any gunk in it that I could see. However, the screen appeared to be sucked flat and collapsed. I opened it up carefully with a small screwdriver and punch. Cleaned everything and put it back together. The few minutes I was able to run it, there was no more jerkiness. The proof will come next time I give it a good workout. Thanks for the helpful tips!

That’s great! There was another guy I remember had his collapse also. I don’t know how that happens, but I think I would replace it. The last thing you want is for that screen to start disintegrating. That would send fragments right into the hydrostatic transmission.
Just theorizing as to a possible reason for collapse…Since that line supplies charge flow to the eHydro system, I wonder if there are times when the hydro pulls a vacuum and the power steering pump can’t keep up with the charge flow. Maybe that causes that filter to collapse. Do you drive around at (or close to) idle sometimes? Maybe bumping the throttle up a bit would help. I like to have the engine running at around 1500rpm minimum.

 

[qstott]

I don’t usually run it near idle. When it starting getting much worse I was mowing and running about 2500 rpms. It’s a head scratcher for sure.

 

[beenthere]

Hope you have a new screen coming soon. It sucked closed for a reason, I'd guess. And that debris that caused it to close, may be going down the line now to who-knows where.

 

[Brown Dog]

My 4720 open station I sold did this same thing.
best I remember it was a hex shaped filter about 3” long I washed the contamination from & fixed the issue.

 

[oldtimer 66]

Some times hydraulic filters get sucked down is because there is moisture in the hydraulic system. In the winter time when the water in the hydraulic system freezes/ crystalizes/ these crystals plug the filter and collapse it. It might not be a bad idea to change your hydraulic fluid. Just a suggestion.

 

[qstott]

I just mowed for about 30 minutes and every thing worked fine! I do plan to change fluid and filters soon.

 

[Richard]

Good that you evidently fixed your issue.

My backhoe was fighting me at one time. Cutting to the end, what turned to be my issue is the seals in the steering cylinder were starting to leak. This allowed the pressure to squeeze to the other side and nullify some of the push that the pressurized side was trying to do.

Rebuilt cylinder and that fixed that issue. Looking at the cylinder would have probably never crossed my mind....it was my brother in law who brought it to my attention.