Odd rockshaft behavior

jeepinator · Jun 24, 2006

I seem to be the king of odd tractor behavior

It just started doing this perhaps 4 operating hours ago. I noticed it when idling and off the tractor doing something. Basically, the hydraulics start hissing (like you are making verrrry minor inputs) very softly at first, and then louder, and then it lifts up an inch or so. Then it's quiet for a period. Repeat. Forever.
Now I am noticing it when moving and doing stuff.
I think, atlough it's really hard to tell, that it's falling very slowly, and cycling back up.
What is causing this?
I think it's getting worse, but can't be without my tractor for the next few months (or so it seems!).
I checked the fluid levels and they are good.

Miller_tractor · Jun 24, 2006

What kind of tractor? Sounds like your hydraulics are building and losing pressure. Start by changing the filter and cleaning the screen in the belly if it has one. Does it have a loader?

jeepinator · Jun 24, 2006

It's a 3520 w/ 300CX.
~120 hours

Thanks for the tip. I'll pickup a filter.
What is this screen you speak of?

browns40 · Jun 24, 2006

Hi jeepinator,

I have a 3320 thats been doing that since day one! Never thought anything was wrong...

It hasn't gotten any worse for sure in 200 hours.

Any other 3x20 owners notice this?

jmt1271 · Jun 24, 2006

guys, my 3520 has around 20 hours. it also makes these odd sounds coming from the area of the 3PH. i havent noticed it lowering or raising, just makes odd sounds from time to time. i just figured it was normal for hydraulic lifts to do so. maybe there is more to it. should i have my dealer(60 miles away) look at it?

billyo · Jun 24, 2006

Although I've never noticed mine lowering, it does make this noise when fully raised. When this happens, I can move the lever just slightly forward and it will stop. It's as if it is trying to raise the rockshaft beyond it's limits.
3320 eHydro - 18 hours. I thought it was just the nature of the beast.

jeepinator · Jun 25, 2006

I put a few hours on it today and it's definately getting worse.

Another observation: Previously, I could leave the 3 point hitch raised and come back days later and it would still be raised (although I always lowered it if I remembered to). Not any longer. It falls inches in minutes.

This would be majorly annoying problem #2 for me.
Good thing for warrantees

Dex · Jun 25, 2006

I have noticed that my FEL creeps down if it is left parked without the engine running. But have not noticed the rockshafts doing it. I will have it checked and get back with you on it. Tractor is at a JD dealer right now having additional hydraulics installed. I

Cidertom · Jun 26, 2006

On my oringinal (2000 mod yr) 4300 I had this problem. It made grading a real pain. It was in dealership under warrenty a few times as it kept getting worse. Turns out that JD had a design issue and issued a PIP. They cleaned and purged the hydraulic systen and installed an in line high pressure filter that took care of the problem. According to the mechanic, the problem is that the rockshaft valve is very picky and any particle causes the leakoff of the cylinder to the point that the rock shaft valve opens and the cylinder picks back up to the set point. On mine it was quite sudden. This is an adjustment about how far the arms droop before the valve opens. The smaller the distance the less movement but more cycling with noise. The larger the fewer but the bigger the correction.

You might want to check to see if you have the HP filter in the hydraulic line going to the 3 point.

Dex · Jun 26, 2006

I spoke to the JD dealer where my tractor is today and they have not heard of this happening with these models. They asked me if I had heard of a fix to the problem. They will check mine out while they have it apart.