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Case Tractors Discussion Forum

Question about 3 point hydraulics

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07-02-2019 20:46:58

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I just replaced the seals on the rock shaft piston on a 430 diesel. The questions is will the 3 point arms only lower if the engine is running? Seems like before the arms would lower with the engine off. Maybe I did something wrong when I had it apart?
Itís not a big deal, as the arms will lower with the engine running.
Any insight?

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John Saeli

07-03-2019 05:15:18

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 Re: Question about 3 point hydraulics in reply to flatpkr, 07-02-2019 20:46:58  
With the advent of the "Draft-O-Matics" the arms will lower w/ the engine off.

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07-03-2019 03:15:38

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 Re: Question about 3 point hydraulics in reply to flatpkr, 07-02-2019 20:46:58  
Va series will drop diffrent valve design. 300 and newer interlock holds arms up,and the remotes are same way.safer in ways,but t times not so.hooking up remotes can be a royal pain

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Joe (Wa)

07-02-2019 22:35:52

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 Re: Question about 3 point hydraulics in reply to flatpkr, 07-02-2019 20:46:58  
I'll only address the 1960 - 1964 430, although this will likely apply to all later models in some way. Hydraulic pump pressure is required to the safety interlock mounted on the side of the control valve to relieve the hydraulic lock on the lift piston in order for the draft arms to be lowered. Obviously to provide that pressure to the interlock the engine has to be running and the pump pumping. This is a purpose built safety to prevent movement of the draft arms when the engine is not running as that would be the most likely time that someone would be working on or around the hitch arms/attached implement.

Before piston seal repairs the reason the draft arms drifted down was that the hydraulic lock on the piston was relieved by leaking piston seals into the transmission sump.

Pic1 is the position of the safety interlock spool when the control valve is in neutral or the engine is not running to supply pump pressure to the safety interlock. Note that the hyd line to the hitch piston is in a hydraulic lock because the ball check is seated.

Pic2 when the control valve is shifted to the hitch lower position, hydraulic pump pressure enters the safety interlock at port "B" pushing the spool left unseating the ball check providing path for the hydraulic oil lock on the hitch piston to return to the sump via port "A" and the draft arms drop by gravity. Port "C" is partially uncovered to keep the pump from being run at relief valve pressure during the lowering cycle.


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08-13-2019 19:46:40

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 Re: Question about 3 point hydraulics in reply to Joe (Wa), 07-02-2019 22:35:52  
I'm have problems lowering my 3 point on my 440. You can read the thread 8-12-2019. Could this be the reason I'm having problems??

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07-02-2019 21:34:04

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 Re: Question about 3 point hydraulics in reply to flatpkr, 07-02-2019 20:46:58  
The 300's have a hydraulic interlock so the pump needs to have flow before it will lower. I would think the newer tractors would be the same.

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