656 Hydro question

TimWafer · Jul 12, 2011

Took my newly acquired 656 Hydro diesel out for its first shakedown run yesterday. Bushhoged a couple acres of tall grass/weeds. Found the radiator clogged up and had to flush it out a couple times. Also took the brakes all apart and cleaned them up so they both worked first.
Now this is the first time I have ever driven a Hydrostatic tractor, at least of this size. My hydrostatic experience has thus far been limited to skidsteers and lawn mowers.
Being that I don’t own any property that isn’t on a hill, one thing I noticed is that when going down hill the transmission seemed to be coasting rather than holding it back like I expected. It seems to go up hill fine and you can override the brakes with the transmission in low range no problem. Just going downhill it picks up speed like it’s coasting. Made me glad I fixed the brakes before hand. I would think this to not be normal. Am I right and if so what is the likely cause?
Thanks
Tim

DeltaRed · Jul 12, 2011

pull the hydro lever back a little when you go down a hill.pull it back slowly-pull it back far enough-it will stop you.another thing-when you are "in the field",put it low range,dont 'work'it in hi.hi is for roading!

TimWafer · Jul 12, 2011

(quoted from post at 00:19:25 07/13/11) pull the hydro lever back a little when you go down a hill.pull it back slowly-pull it back far enough-it will stop you.another thing-when you are "in the field",put it low range,dont 'work'it in hi.hi is for roading!

Thats just it. Pulling the lever back didnt slow me down much. It seemed to continue rolling even all the way back to neutral. Eventually it seemed to stop but not for a long ways.

Owen Aaland · Jul 12, 2011

Snap ring came off the end of the shuttle valve.

504 · Jul 12, 2011

That is not right, mine holds on a hill fine in low, and in high range.

TimWafer · Jul 14, 2011

I tried it out again on some hills just to be more exact in how it behaves. I have only really used it in low range thus far except to make sure high range worked. I have not taken it out on the road yet and likely wont soon.
The following were done without the use of the brakes.
When descending a moderate hill and pulling the hydro lever back to neutral it will continue rolling forward for another 30 to 100 feet before stopping. When descending a steep hill it continues rolling to the bottom. When descending a hill and leaving the hydro lever at the same setting it picks up speed.
It climbs hills fine and there seems to be no slipping or hesitation at all while ascending.
In low range with the brakes applied you can easily override them with the hydro.
I don’t yet have a service manual (ones on the way) but thought that maybe there was a relief valve or something that was allowing it to do this. I dunno?? I will look for the snap ring mentioned.
In my skidsteer and hydro mower when you move the levers to neutral it stops immediately. Thought that this would behave similarly.
Tim

TimWafer · Jul 14, 2011

Looking through the IH parts website I see a 404211R91 Decelerator relief valve listed for the 656 hydro. Can anyone tell me what its function is or where it is located? Sounds like a likely culprit by the name.
Sure wish that manual would arrive.
Tim

Owen Aaland · Jul 14, 2011

(quoted from post at 15:04:07 07/14/11) Looking through the IH parts website I see a 404211R91 Decelerator relief valve listed for the 656 hydro. Can anyone tell me what its function is or where it is located? Sounds like a likely culprit by the name.
Sure wish that manual would arrive.
Tim

The Decelerator relief valve is working. That is what caused the tractor to slow when you pulled the lever back to neutral.

The most likely cause of your problem is the snap ring is off the end of the shuttle valve. The shuttle valve is what the directs the charge pressure to the unloaded side of the hydro circuit to provide make up oil to keep the circuit full. The valve is spring loaded to the center position and moves to supply the oil to the intake side of the hydrostatic pump. When going down hill or decelerating the motor and the pump swap functions. If the shuttle valve does not shift then the hydro circuit will not stay full of oil.

TimWafer · Jul 14, 2011

Owen
Where is the shuttle valve located then? Thanks for your help!
Tim

Owen Aaland · Jul 15, 2011

On the left side of the center section of the tractor there are two 1/4" steel lines. Behind the rear one is a large pipe plug with a recessed square hole. remove that plug and the end cap for the shuttle valve is just inside. Remove the end cap carefully because if the snap ring is off or broken there will be some loose parts. Usually all it takes is to install a new snap ring and reassemble.

A more common complaint with the snap ring problem is that the tractor will not go backwards unless you first move the lever forwards or use the Foot-N-Inch valve. When it does go into reverse it does so with a jolt.

If the snap ring is not the problem then you need to isolate the hydro unit from the outside controls by disconnecting the two high pressure lines and cap them. If you do this be sure you have plenty of room around you because the Foot-N-Inch valve will no longer control the tractor. The only control will be the SR (Speed Ratio) lever. That test can determine in the problem is internal or in the outside controls.

656 Hydro question

TimWafer

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DeltaRed

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TimWafer

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Owen Aaland

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504

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TimWafer

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TimWafer

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Owen Aaland

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TimWafer

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Owen Aaland

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