[sandroost]

2022 TYM 574 with only about 30 hours on it. Something isn't right out back.

When the 3 point is loaded with pretty much anything, while running, it will slowly drift down about an inch maybe two (at the back of the rotary cutter) then "catch itself" and bounce the implement back up to the set height. At higher rpms, it's a somewhat violent jerk back up to the set height, bouncing the whole tractor. At idle it is a slower correction and much less noticeable. When mowing, it's harder to tell when it's jumping back up, but it seems that I can tell when it had sunk judging by the cutting height of prior passes.

If I close the rate control valve, it won't sink at all under heavy load, and with a light load with the engine off, even overnight, it won't drop at all. But if the rate control valve is open to any degree, it'll sink, running or not but might take longer.

I'm planning a routine service soon, will certainly mention this to them, and it'll be interesting to hear what they have to say.
But I would like some insight from others here who might know whats going on, so I might know if what they say is the straight poop, or hogwash.
Thanks all.

 

[BinVa]

Do you have a draft control setting that’s causing it adjust? B

 

[unsquidly]

Do you have a FEL on the tractor? If so, is it acting up at all? Also, have you checked the hydraulic fluid level?

 

[sandroost]

I have draft control, and don't know how that might affect things. I'm completely ignorant about draft control ....
I have FEL and it's working just fine. Fluid level is good.

 

[BinVa]

Your draft control is compensating for the load on the 3pt. Either shut off the draft or raise draft lever to full up position,this should stop the jumping. B..

 

[sandroost]

Thank you BinVa. I'll give the draft lever all the way up a whirl

 

[sandroost]

Tried that first thing this morning- draft full up, started the tractor, left at idle, raised cutter, and all held fine for a few minutes. The it started to sink/pop up at about 30 second intervals.

 

[Vigo]

I think it has to do with position control, not draft control. The 3pt is sinking and because you have position control it is correcting itself.

So just gotta figure out why it’s sinking. Closing the ‘rate’ knob is a good clue because if it was leaking past the 3pt piston rings the rate knob wouldn’t affect it, so not leaking at the piston!

If it’s not leaking externally, then you have already narrowed it down to a pretty small range of possibilities because the entire hydraulic circuit from the 3pt cylinder, through the 3pt valves, rate control valve, back to sump etc is probably contained within about 1 foot of space on the tractor. It has to be something after the rate valve, that can leak into the sump..

Next step would be to look at some diagrams and see what COULD do that, and go inspect it.

 

[Tx Jim]

My guess is 3pt control valve is at fault for variation in 3 pt height due to sandroost stating when R-O-D screw is closed 3 pt stays where set.

 

[sandroost]

Thanks for the input guys.
Hopefully the dealer sees it the same way, or clearly another way, and fixes it.
It's a little unnerving when I get lightly bounced in my seat unexpectedly, say when say focusing on picking something up with the FEL. Or when walking around the backside of the lifted (PTO off, duh) cutter and it bounces.

 

[Tx Jim]

If dealer doesn't correct your tractor's 3 pt hitch hiccupping you could add a device similar to Rooster comb used on older Ford N series tractors that would limit how far down 3 pt hitch can travel.

 

[Busted Tractor]

There is more than likely a leak between the control valve and the lift cylinder to include the cylinder. The tractor also has follow up hydraulics, which means there is a link between the rockshaft and the control valve. The valve then senses when the hitch drops and brings it back to its preset height. Some "cheaper" tractor have no follow up and if the implement drops it will go completely to the ground or the operator has to raise it back up.
As stated it should have nothing to do with the draft linkage. Draft is used for ground engaging implements. Draft control maintains an implement at a operator set depth. Position control sets the height at where the operator sets it and should hold it at that point.
Some pistons on the hitch lift are sealed with O rings and should not leak or leak very very slowly. So pistons use steel rings like piston rings in the engine. These tend to leak down to to the ring needing an end gap and the usually don't seal to the cylinder as well as O rings.
Most folks want to blame the control valve when a load is not held to a specific height. The control valve should be the LAST place checked, they will not usually cause a load to leak down unless they are internally damaged or are cracked and leak oil outside. The only thing O ring do in a valve is keep oil from leaking to the outside, they seal nothing internally.
My thoughts would be either there is an internal leak or the rings on the lift cylinder are leaking.

 

[sandroost]

“Most folks want to blame the control valve when a load is not held to a specific height.”

Well, my dealer/mechanic falls into the most people group on this as they replaced the control valve. So we’ll see….
They still have it and evaluating how it’s working today🤞🏻