Help with 3PH/ Rockshaft bleed-down

Titleman

New member
Good day to all.I need some help figuring out how to keep my 3PH from bleeding down when I'm using my bush hog. When I raise it completely, it very slowly bleeds back down a few inches, then recharges or lifts back up and the process starts over again. It only takes about 30 to 45 seconds for this to do a complete cycle. Very annoying and it sorta jerks the tractor alittle when it recycles. A few of my friends, none of us being mechanics, say, just take it back to the dealer. I purchased it new in July of '07.It's an '06 3720 John Deere. I have a 295 Bush Hog on it that weighs 910 lbs, according to the manual. It doesn't keep us from using it but, it is annoying and can think of nothing good that could become of it. Any and all comments on how to correct this will be greatly appreciated. I know I should read up on it more through my manuals but....., I'm trying to help the forum by posting a question, and besides. I like to hear different points of views, not just the printed variety. Thanks, Tom
 
B

bczoom

Guest
Some bleed down is normal. With that kind of weight off the back, it does seem fast but be it 30 seconds or 30 minutes it's still going to occur.

It's been many years since I put cutter/mower behind my tractor but think I recall a work-around for the issue.

If your JD is similar to mine, there's a knob in front of the seat (or somewhere) that controls the rate/speed of drop for your 3PH. When open, your 3PH will fall like a rock when you lower the control arm. I just closed that valve/knob all the way which greatly diminished or completely stopped the unintended bleed down like you're experiencing. It's worth a shot... BTW, you'll obviously have to open it some to lower your implement when the time comes.
 

Doc

Admin
Staff member
Gold Site Supporter
I had a old 8N that I could not keep the brush hog positioned right while hoggin. My solution was chains that mounted to the tractor and stoped the brush hog from going any lower. I would set those to the height I wanted to cut. It worked like a charm. I found the plans for making the chains on a site called Yesterday's tractors. I just looked and do not have them on this computer. I'll check and see if I can find the plans on my computer at home.
 
Sounds like a relief valve leaking off or possibly the position control valving or the lift cylinder itself leaking. I'd bet on the relief valve myself. Sorry to say, but in most cases, unless you're VERY "hydraulic system savvy", that's a dealer job.


edit; Is it doing this at idle speed, or will it do the same thing at higher rpms?
 

Mith

Active member
When you say it drops and lifts, it lifts by itself when it drops to a certain level?
I'm not familiar with draft or position control, but could it be an issue with one of those? If it was just leakdown it wouldn't re-lift itself.

If its got warranty left, I'd let the dealer sort it. Its possible that if you mess with it yourself you might have a problem claiming on the warranty further down the line.
 

Titleman

New member
I had a old 8N that I could not keep the brush hog positioned right while hoggin. My solution was chains that mounted to the tractor and stoped the brush hog from going any lower. I would set those to the height I wanted to cut. It worked like a charm. I found the plans for making the chains on a site called Yesterday's tractors. I just looked and do not have them on this computer. I'll check and see if I can find the plans on my computer at home.
Thanks Doc, I'll also check out "Yesterday's Tractors" site.
 

Titleman

New member
Sounds like a relief valve leaking off or possibly the position control valving or the lift cylinder itself leaking. I'd bet on the relief valve myself. Sorry to say, but in most cases, unless you're VERY "hydraulic system savvy", that's a dealer job.


edit; Is it doing this at idle speed, or will it do the same thing at higher rpms?
Farmwithjunk, I'm certainly not" hydraulic system savvy", so I'll probably end up taking it to the dealer, unless, like bczoom said, I can adjust it out using the knob for that purpose. Yes, it does it at all RPMs. Just alittle faster the higher the RPMs. Thanks , Tom
 

Titleman

New member
When you say it drops and lifts, it lifts by itself when it drops to a certain level?
I'm not familiar with draft or position control, but could it be an issue with one of those? If it was just leakdown it wouldn't re-lift itself.

If its got warranty left, I'd let the dealer sort it. Its possible that if you mess with it yourself you might have a problem claiming on the warranty further down the line.
Mith, thanks for trying to answer my cry for help. Yes, it lifts by itself each and every time, immediatly after it drops about 3 or 4 inches. I know that over time, some if not all, will bleed down. Also, I do not have draft or position control, that I know of. I've looked through my manual and I'm pretty sure it does not. I will do what bczoom said and try to readjust it using the "Rockshaft Control Knob". I made the statment in my original post saying I had purchased it in '07 when in fact, I purchased it in '06. Yes, it's still under warranty. I'm sure it's something I've done to make it react this way and in due time, will figure it out, thanks to good people such as yourself and many others on this site. Gosh, I like these tractor forums!!! Thanks again, Tom
 

Mark777

Member
IMO...and like farmwithjunk stated, I think it's the in line pressure relief valve too. It sounds as though it's cycling rather than opening and closing at normal operation.

If there is debris in the hydraulic fluid, that's enough to cause problems, clog O rings and foul your filter....It may be as simple as that.

Good luck and keep us informed.

Mark
 
Mith, thanks for trying to answer my cry for help. Yes, it lifts by itself each and every time, immediatly after it drops about 3 or 4 inches. I know that over time, some if not all, will bleed down. Also, I do not have draft or position control, that I know of. I've looked through my manual and I'm pretty sure it does not. I will do what bczoom said and try to readjust it using the "Rockshaft Control Knob". I made the statment in my original post saying I had purchased it in '07 when in fact, I purchased it in '06. Yes, it's still under warranty. I'm sure it's something I've done to make it react this way and in due time, will figure it out, thanks to good people such as yourself and many others on this site. Gosh, I like these tractor forums!!! Thanks again, Tom

On my Allis-Chalmers I have draft control and what you describe is almost identical to using draft control turned on when using anything that doesnt engage the ground...like a plow or a disc. Draft control is designed for ground engaging elements. Its a pain in the a** on anything else like mowers and such because it will do just what you describe. And when you are bush hogging it makes it look like waves....:angry: in the ground you have gone over. It sucks. Hope you find out from the dealer.
 

dsgsr

New member
This has been my experience, JD had numerous problems in the 4xxx series with the 3pt control valve and changed out many because the internal O-rings were inferior allowing leakage. BUT also some of the problem wasn't the control valve, it was debris such as Milling shavings in the housing that were not properly cleaned out at the factory and these scored the cylinder wall of the hydraulic piston that operates the 3 point hitch. The piston has an O-ring and the score tears the o-ring and can cause the leakage which happen in My case. I bought a JD 4700 New in yr 2000, it had (what I call a hiccup in the 3pt hydraulics from the start. I took it back to my local dealer every yr for this problem and every time they would replace the control valve. SO after the fourth yr the JD rep. let my local dealer open the 3pt housing and LOW and BEHOLD they found a score in the cylinder wall. Well I thought (stupid me for thinking) they would replace the housing and all would be fine, They didn't. They honed the wall, replaced the piston and O-ring and in the spring when I started bush hogging (this is when it happened the most) it started all over again. I took it back to the local dealer and they contacted the JD rep. and he said (owner abuse) Well it's out of warranty so What can I do short of hiring a Lawyer which I don't have the $$ for. Thats my story and I'm sticking to it.


David
 

Doc

Admin
Staff member
Gold Site Supporter
dsgsr,
Sorry to hear about that. That is truly horrible.

titleman,
I did not find the limiting chains diagram. I'm sure I could find some on the internet .... but I didn't realize how new your tractor was. It does sound like it needs fixing. Good luck getting it taken care. Keep us posted.
 

Titleman

New member
Yep. Has the fluid been changed? How many hours are on it?
bczoom, thanks for replying; the only change of any fluids has been at the 50 hr, service interval and it only has 77.4 hrs. as of today.
On my Allis-Chalmers I have draft control and what you describe is almost identical to using draft control turned on when using anything that doesnt engage the ground...like a plow or a disc. Draft control is designed for ground engaging elements. Its a pain in the a** on anything else like mowers and such because it will do just what you describe. And when you are bush hogging it makes it look like waves....:angry: in the ground you have gone over. It sucks. Hope you find out from the dealer.
I'm pretty sure draft control is not on mine. I have not found a switch, knob, handle, lever, button, dial or whathaveyou on it for that purpose.
Sorry to hear about that. That is truly horrible.

titleman,
I did not find the limiting chains diagram. I'm sure I could find some on the internet .... but I didn't realize how new your tractor was. It does sound like it needs fixing. Good luck getting it taken care. Keep us posted.
Hi Doc, thanks for checking on that for me. I'm going to tinker with it this weekend and if nothing come of that, then I'll load her up and back to the dealer she goes. Tom
 

Titleman

New member
I was going to adjust the rockshaft knob this past weekend and while warming her up, I raised the RC and noticed that it was not doing it (bleeding down) anymore:biggrin: . The tempurature was chilly, enough for a jacket but, not cold cold (don't remember actual degrees). Do any of you think the weather had something/ anything to do with this behavior? Talk about :confused: . It's going to be around 31 degrees this weekend here and I will be back on it tomorrow. I imagine I probably shouldn't worry so, huh? Thanks, Tom​
My toothbar arrived today and will try and install and use some if all goes well.
 
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