Hydrostatic Chatter?

[BigDogues]

Hey guys, I seem to be getting some chatter, for lack of a better term, from my HST. This usually happens when I am running full tilt, in low range, up hill and usually from take off. Some of you that have HSTs may have experienced something similar if you push your tractor too hard in a higher range. But I am kind of surprised that I get as much as I do in low range. It does seem to smooth out after I get up to speed. I also seem to be noticing more "groan" when the pedal is initially depressed on take off or when I am pushing a load with it. Rule of thumb says to back off on the pedal to get more torque right? But if I do that I just get more groaning.
My hydraulic oil level is right up there. If any thing maybe a little too much so. I had been keeping it a little on the high side so I wouldn't run low when I use my dump trailer. Could this be causing this chatter or is there something that needs to be adjusted on my tractor? Or am I just expecting too much from my 25 hp tractor?
I'll probably drain some out to see if it makes a difference, but I figured I would ask for your input anyway. /forums/images/graemlins/grin.gif

 

[KiotiJohn]

Not that I can really know what chatter means, but it sounds like you may be experiencing an intermittent relief valve problem as though it is going in and out of relief. It shouldn't be doing that, but that's what it sounds like to me. The RV is operated and is set to pressure with a spring.

A little high on the hydro fluid shouldn't cause much of a problem, but if you're way over, you may be experiencing foaming of the fluid which would cause it not to operate correctly. Don't go above the top line from the end of the stick, that's high range. Try to be between the lines optimally.

John

 

[BigDogues]

Thanks KiotiJohn,
Hmmm, can that relief valve be thrown out of adjustment by a stray branch or something? I wonder if it has vibrated free and is steadily becoming worse? That could explain things. How would one go about tweaking it back into position? Any idea where it is located? I'm suppose I more concerned about burning up the HST than anything. Is that a possibility? /forums/images/graemlins/shocked.gif

 

[KiotiJohn]

Well, there are more than one of them, and I'm not sure of all the placement without the service manual, which I still haven't picked up.

I'm not sure that that could happen by a stray branch, but could be that it was a weak valve spring from the beginning or not seated just right I would suppose.

Try this just in case it's an air problem.

While the tractor is running, if it starts chattering, stop moving. Run the loader up some, and through all it's various moves, then power it down to the ground and let it sit there for 30 seconds. Don't just push it into float (all the way foward on the joystick till it locks).

If for some reason you have a cylinder or other part of the system that would allow some air in, floating the loader down instead of powering down could suck some air in. The procedure above should bleed the air out.

After you've sat for the 30 seconds, try it again and see if it still chatters.

I'm going to PM you my phone number, call me when you get a chance after doing this okay? There are some things I want to ask you, easier than typing.
John

 

[VictorW]

My CK30hst has what I'd call a chatter but only after startup. It does it when the tractor sits overnight. After initial startup and warmup, the first time you press the pedal to go, you feel a vibration in the pedal. It lasts for about a few seconds and then it's gone. It doesn't return unless the tractor sits overnight again. Other than that, I feel it in high range like you mentioned but then you're working the tractor hard so it's to be expected. Never felt it in low range even when pulling a really heavy load.
How long since you changed the hydro filter? Maybe you are getting some foaming like KiotiJohn mentioned.

 

[BigDogues]

Yes that is what I am trying to describe. It's sort of feels like a slip/engage thing that's happening at a very rapid pace and lasts for a few seconds on take off. The problem is that it doesn't go away after the tractor is warmed up. My tractor only has 73 hrs on it and I did a full oil/ filter change at 50.
I haven't drained the extra oil out of it yet. I'll probably do that this weekend. I hope that's all it is... /forums/images/graemlins/confused.gif