2955 John Deere Hyd. shake

Stupid Tractor Mechanic · Mar 30, 2010

tractor has new hyd. pump. scv boxes run loader bucket and loader lift cylinders, and the hoses and loader shake violantly as if there is air being introduced in the system during loader operation, there is no problem in the steering or the 3- point lift. Had same problem before new pump, now seems even worse due to more flow from the pump. Have checked flow and pressures and all are okay. any one have any ideas were the problem could be coming from.

justanothercase · Mar 30, 2010

Had this problem on a different tractor and it turned out to be the return wouldnt flow enough oil.

hope that helps have a good one

Stupid Tractor Mechanic · Mar 30, 2010

Thanks for the reply I hadnt thought of that one it sounds like it could be a possibilty that the system is being starved, thanks again.

RodinNS · Mar 30, 2010

Is it making adequate charge pressure at rated flow? I'm suspecting that ti isn't...
Mabey a leak. Mabey a plugged strainer?

Rod

BCnT · Mar 30, 2010

i just went thru that mess with my JD dozer...look for a screen inside your hydraulic tank on suction feed...mine was filthy and doing exactly what you describe...i honestly thot the pump was going out.

Tx Jim · Mar 31, 2010

(quoted from post at 22:23:01 03/30/10). Have checked flow and pressures and all are okay. any one have any ideas were the problem could be coming from.

Exactly what was trans & main hyd pump flow& psi? Have you changed hyd filter & checked sump screen?

tjdub · Mar 31, 2010

I have a 2950 and the same thing happens to it from time to time. The cause is an internal low pressure leak. The hydraulic fluid flow from the transmission pump to the high pressure hydraulic pump is inadequate. When it happens to me, I make sure the Hi-Lo is in Lo, increase RPM and run the loader all the way up and down and it's fine.

The real annoyance is trying to run a hydraulic motor with it when this happens since instead of bouncing it trips the lever off. Again putting the Hi-Lo in Lo seems to make this happen less often.

Anyway, make sure to clean your screen and change filters if you haven't done so recently. Cleaning the screen on mine made a big difference (it was covered with bits of hay).

Stupid Tractor Mechanic · Mar 31, 2010

Hyd. standby pressure is 2000 and when control valve is operated it goes to the recommended 2350. even with new front pump flow is only around 9gpm. has new Hyd. filter and cleaned sump screen, did find some debris but nothing even close to slowing flow. Do not no the procedure for checking Trans. pump flow.

RodinNS · Mar 31, 2010

To check the charge pressure and flow properly you'd need to plumb a flow meter into the charge line along with a pressure gauge and then place the remotes under full demand and check to see what flow and pressure you have in the charge system.
I'm not familiar with the specs for that tractor but I'd wager that the flow should be probably 130% of the rated system flow on the main pump AT probably 165 psi or in that range.
If you don't have a flow meter but do have a gauge I'd say a quick and dirty check would be to plumb the gauge into the charge line or manifold somewhere, rev the engine to half throttle or so, then place the SCV's under full demand so that the main pump fully strokes.... THEN oserve the charge pressure. Again, I'd expect it to be in the 160 psi range. If it's not up there or it recovers when demand is removed from the SCV's that would indicate a leak somewhere in the CHARGE circuit. Possibly in the Hi-Lo or the tubing through the transmission. Possibly just a weak charge pump...

Rod

JD Seller · Mar 31, 2010

Running a loader through the SCVs on a John Deere is quick way to mess up the hydraulic system. The transmission, or charge, pump is in the 5-6 gpm. The main pump is 16-20 gpm. So you are starving the main pump for oil. The loader is supposed to have an external valve that returns the oil to the filter cup. That way the charger pump doesn't have to handle it. Loader will work faster and quit making noise.

buickanddeere · Apr 1, 2010

You said scv's? Who in thier right mind is fooling around with scv's and a loader,backhoe,log splitter or hydrualic motor? In particular wiht a Mannheim or Dubuque Deere.
Plumb it in correctly with a joystick supplied direct from a "T" in the high pressure line. Then return the oil through a ported filter cover.
You have spent how much time and money guessing and replacing parts that were working?

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