304 TPH Issues/Questions

[Rich Waugh]

Hey guys, I have an issue with my TPH that I'd like some guidance on. My 2007 304 Jinma has the single-lever control for the lifter; top half of the movement is position control and lower half is draft control. That's all well and fine, I understand the difference and applications thereof, but the position control is a bit too arbitrary to suit me.

If I have the bush hog on and raise the hitch up I have to pull the lever nearly to the top of the travel to get it to initiate movement, then it goes right up. When I want to lower it to cut, I have to drop the lever nearly to the bottom (of the position control portion) before it even starts to drop, at which time it goes down pretty much all the way. I can finesse it into the position I want by going back and forth until I get lucky, but that isn't really too handy, you know? I'd like it to be more "linear" in action (more determinate, so to speak), so that when I move the handle a little bit I get a little bit of TPH movement - in a predictable way. Not this random chance routine I have to use at present.

So, what's the answer? Do I simply need to adjust something, or have I somehow along the way screwed the pooch and need to rebuild the lift cylinder? I'm thinking the cylinder itself is okay since it stays up when it's supposed to, even when I'm bouncing all over on rough trails. Is there something that needs to be done to the control valve for the TPH?

I'd like some direction before I just blunder into this since I'm not a wizard with hydraulics - I understand the theory, it's the practice I fall down at. In theory, there's no difference between theory and practice - in practice however, there is.

I await enlightenment!

Rich

[GuglioLS]

Hi Rich,

My 2005 354 has two levers, one for draft and one for position so I'm not going to be much help on this one. What I can say is the "precision" of my position control is not much better than what you describe. When I move the lever up, there is what I call a "delay" meaning I have to overshoot before it starts to lift, then of course it overshoots where I really want it to go. However when lowering it's "fairly" precise in that is starts going down as soon as I lower the lever. I've learned to live with the fact that Chinese hydraulic controls are not all that great (POS in fact). The TPH position control on that old ford of mine is super smooth and precise in that is has instant predictable response. Of course I mounted that back hoe on it so I never use the TPH any more . I doubt your cylinder is in need of any rebuilding but rather the valve contraption that is supposed to control the position is perhaps somehow gummed up or otherwise of lousy design. Did it ever work "right" or has it always been like that? Is the lowering speed control knob under the seat all the way open? Have you fiddled with the setting on that to see if there is any difference in lowering precision? Perhaps Tommy or Ronald may have better advise on that.

[Rich Waugh]

Thanks for the input, Larry. I've been hoping you or Rob would weigh in with some guidance. As I noted, hydraulics are a bit over my pay grade. To answer your questions: No, I don't recall it ever being much better than it is at present. Yes, I did spend an hour fiddling with the flow control valve and got it so it is a bit more acceptable. It was wide open, i.e.the mower dropped like a rock, and when I closed it down a good bit until the mower dropped moderately slowly I could finesse the location somewhat better.

I would just like the damn thing to be proportional - you know, I move the lever 20% of travel and the implement drops 20% of the way and so on. Not the case - mine is pretty much like yours. I have to overshoot and before it moves at all and then back off to end at the "right" place. I suppose I'm asking a bit much of the Chinese hydraulic control circuitry.

Unfortunately, my manual only shows the old-style with two levers so it ain't much help. That's even if I was good at reading drawings, which I'm not. :-) It does look like there's supposed to be a feedback circuit with a spring and and all kinda like a regulator circuit, but it all means squat to me. I'm not about to disassemble the thing unless I have MUCH better idea of what the hell I'd be doing. Yeah, I'm timid around stuff where I'm in completely over my head with no way back out.

Rich

[bradblazer]

I don't have a lot of experience with this but can you pull the cover off, maybe drain the reservoir box, and just take a good look at the mechanism to see if anything looks screwed up?

[Rich Waugh]

Not sure about that, Brad. It's raining like hell right now and has been for a couple days, so working on the tractor right now is not on the menu. I'll Probably be needing it after the rain quits to move some earth back where it should be.

We're under flash flood warnings right now so it will be a couple days before I can do anything with the tractor.

Thanks for the suggestion!