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tistab

Hydrostatic trans low pressure

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tistab

I have a mid 70's allis 916 with the sundstrand 15 hydro. this tractor has been running satisfactorily until I added power steering which I robbed of a working Sunstar. Now the tractor surges and the power steering is very slow. I rechecked all the hose routings and I have the hoses connected correctly with the aux routed to the 'in' side of the lift valve and the steering 'out Teed into the lift 'out' Believing the pressure low I have put a pressure gauge in the steering cylinder hosed and basically i have nil pressure reading on my 5000 lb gauge. today i checked for a sheared pin in the charge pump and the relief valves for bleed down. everything checks out. Does anyone have any ideas, am i do for a Hydro rebuild ? If so where can I get parts..thanks, Dennis

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D-17_Dave

You also need to swap the relief valves off the unit that the steering came off of to properly direct the oil to the aux circuit. Rod Hubbard has a diagram on how to do this properly. Do a search under his name to find the link to the post. And welcome to the club.

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tistab

Thanks for the reply and information. I will pull the side plug and add the necessary valve and spring. I have the charge pump pressure side piped into the steering pressure port and then the aux port on the power steering unit goes to the lift valve. Is this correct. The only t is in the return lines from the steering and lift valve back to the hydro

Thanks again

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PhanDad

It sounds like you have the PS plumbed correctly. Here's a link to the Sovereign PS install instructions (mfg#1692856):

http://bsintek.basco.com/BriggsDocumentDisplay/default.aspx?filename=jgEBGP_dqH5tG7EPl7mRgtLvBCd6

Here's another great post about calibrating the charge pump pressures:

http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=117631&SearchTerms=calibrating

From your initial post, I'm not sure if your tractor already had a hydraulic lift. If it did, you shouldn't have to add the extra relief valve. And make sure the hydro fluid is full, sometimes they drain down when sitting and if you check, it appears full but it's really not.

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tistab

D17 Dave and Phandad, thanks for the response. Yes it has implement lift. I pulled the side plug and there is a spring and valve. Its a much stiffer spring than in the top valve. I am now proceeding to read the caiibration links.

Just in case, has anyone done a hydro rebuild and if so what is the source of parts, such as the seals, pump , motor and charge pump.

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Brettw

I have been told, that the Sundstrand pump on the Sunstar is the same pump as used on the Sovereign. I would think that the shafts are differerent, but I'm just tellin' ya'll what been done tolt.

As far as rebuild, I think that's 'spensive. A used pump might be the wat to go. I think if you didn't have issues before, when properly valved you shouldn't have issues now. The Sunstrands are known to be pretty bullet proof.

Or not.:o)

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MysTiK

They are all Sundstrand 15's. Some have hoses to remote filter; others have filter on the left side.There are co's that rebuild them. But usually people replace w used.Proper procedure for checking fluid level involves start COLD and run for 30 seconds - don't check it hot. (expansion, spillage, messy) btw your 900series tractor is more likely a mid80's or it would be a 700series from mid70's - same trans. sm01Below is instrux copied from page26 of the AC700-series manual for ATF fluid check on Sundstrand 15 Hydro. (This manual is available from /Simplicity site /Manuals using MFR 1690211).= SEE ITEMS A THRU F = ...

HydroFluidCheck.jpg

HydroFluidCheck.jpg.5ffba71f522136de19172cd0af8fe60e.jpg

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tistab

Thanks to everyone on their replys. today I was able to procure the proper springs for the implement relief and pump. I borrowed them from another working tractor with implement lift. Now I have a very slow tractor and still nil pressure on the gauge on power steering cylinder,which is confirmed by the very slow movement.

Anyone have any ideas or is my hydro out of power.

Thanks

Dennis

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RayS

did you use those shims from the other tractor. they are between the springs and the pipe plug. I done two powersteering / hydraulic lift systems and you need those shims. they are more than likely wedged in the plug - cap that screws in to the housing.

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RayS

If you borrowed the springs from a tractor with implement or hydraulic lift. Then there in the caps or the plug that holds the springs in the housing. The hydraulic tractor won`t lift much without them.

When I did my two tractors, I used the plugs from the hydro lift tractor as well. Then I simply moved the plugs and other parts to the non hydraulic lift tractor.

The link below has the part numbers needed. They are available through a Simplicity. Not sure what manual Rod got the diagram from, but I will see if I can find the manual when I get home.

http://www.simpletractors.com/club2/topic.asp?ARCHIVE=true&TOPIC_ID=106418&SearchTerms=power,steering

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acfarmer

I'd crack the fitting connections at every place I could as it seems like you have an air lock somewhere.Even with low pressure or volume it should work as good as it did before as long as you're only one thing at a time,where vloume comes into to play is doing 2 or more operations at once.Also may be an obstruction in the line somewhere which could have gotten there when you had the lines open or you stirred up something that was stuck in place in the system.I had a

hydraulic system suck a large "O" Ring once and it was a nightmare getting all the pieces out.

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CarlH

Graham you are correct that the Sunstar and Sovereign hydro's are Sundstrand Model 15's. Note that the Sunstar hydro has splined shafts while a Sovereign hydro has keyed shafts. They are the same basic Sunstrand but different spec's.

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tistab

CarlH and ACFarmer thanks for the feedback..I am now thinking that possibly the hydro was weak prior to the PS install, and now the charge pump is overwhelmed with the additional work. I still plan on draining the system and a new filter and bleeding for air before I give up hope.

I see a NOS Cub Cadet Model15 Hydro for sale on ebay. I am tempted to buy it and rob the rotating elements and charge pump out of it. Any thoughts on this. A parts source quoted me $500.00 exchange for the rotating element alone. I see used hydros for sale but I am hesitant about buying one that I dont know its history....

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MysTiK

I think a pressure guage w a much lower range would be useful. I have read it is possible to crack the hydro cases at max pressure 800 lbs. You will likely end up using a pressure of 700ish lbs. on the lift circuit; but not on the drive circuit, where pressure will be considerably lower, and even harder to read.

You have said that your 5000 lb guage shows zero - and things are still working, altho slowly, or barely. Since you are going to be operating two different pressures, and one is slightly below max pressure, I would think it important to have a more readable, more accurate guage; before the limits are exceeded. I am thinking a guage in the region of 1000 lbs might be very accurate. This is all about controlling and fine tuning 2 output pressures, assuming all else is well.

I also think a fluid change and a new filter will nicely standardize the entire system - just to make sure all that is good to go. Also you will then know what fluid is in it; and that the fluid and filter are clean, and not affecting results in some arbitrary manner.

(i.e. standardize, or get a handle on the beast) (I can post fluid change procedure if needed).

= @ CarlH = (thx Carl, for info - that's news to me - not sure what it means however, assuming that's about internal hydro shafts??? - but don't want to sidetrack this busy thread, unless necessary. thx.)

.

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MysTiK
quote:Originally posted by tistab

Thanks Mystik. I just ordered a lower range gauge to use for test and measurement on a hydro.


id="quote">
id="quote">Good to hear - now I can sleep easier. sm03

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CarlH

Graham, Brett,

The input shaft from the motor and the output shaft to the rear PTO are splined on the Sunstar hydro. It is actually the same shaft. The Sovereign hydro input shaft is a keyed input shaft (the drive pulley mounts on it) and it has no equivalent output shaft. This means the Sunstar and Sovereign hydro's are not interchangeable without changing that shaft, at the least.

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MysTiK

Carl, that's very good info - thank you.

I did not realize that important difference with the Sundstrand spec. in the Sunstar tractor. dOd First I have heard of that. Sunstar is a unique beast in a lot of ways.

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tistab

CarlH makes a good point about switching transmissions between brands and models. In my search I have seen various configurations of the input and output shafts.

Most likely the internals are the same and if you were to obtain A good trans from another tractor it would mean a tear down to switch the shaft(s) from the old trans.

But I have no way to confirm if the internals are the same. Has anyone done this ?

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acfarmer

The Sunstar and the John Deere 420 and 430 are very similar tractors with different engines.Rears and hydros are basicaslly the same.Sunstars have alot more in common with Deere tractors than they do with Simplicity built units the 18HP Sunstars and the Deere 318 have the same single speed rear and hydro.All of them Deere and Sunstars are excellent tractors BTW.

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