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rickpilgrim

Hydrostatic problems in 912 AC help needed

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rickpilgrim

First off our AC 912 is more like a 7117. We have added the hydralic lift of a 7016H, shimmed the relief with dealer supplied shims and more, and has a sick Robin 20.5 engine that has maybe 16 hp. It also sat non running from 1998 until very recently.

Before putting motor back in we drained and refilled the bgb, put a new belt on, drained hydro and filled with AW32 trans hydralic fluid and a new WIX filter.

Even with the dealer supplied shims for pressure it will not lift the snow blower. In fwd and reverse it seems very solid but no mater what will not spin the fluid filled 10.50 tires unless against a wall.

More alarming is when checking the level of hydralic fluid after shutdown it spit a pint of fluid out with the check stick, it seemed very overheated but 10 min run time should not have done that.

My first thought is to get the NAPA recommended AW32 out of there and replace with some 15w-40 oil, and a different charge pump as work empty but no lift on snowblower.

Ideas anyone?

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RayS

Why not just put the recommend oil in it?

sunstrandoil.jpg

The diagram suggests the recommend fluid. You sure the hydraulic lift didn`t come from a 7116H? They never put hydraulic lift on a 7016H. If they did you have a very rare 7016H or the previous owner done it himself. I always overfill mine and just let the extra run out into a oil pan why it is running. When it is done, I just put the cap on.

sunstrandoil.jpg.1e6ffc6d18c8976d1a3bfa5dbc34c80d.jpg

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rickpilgrim

I trusted the NAPA guy when I got the WIX filter when he said AW32 was the recommended fluid for all AC garden tractors.

AW32 is about a 10wt oil designed for hydralic transmissions and tractors, and it is rated as an equivalent fluid for our Toro Groundsmasters with sundstrand hydro's and works great in the Toro's in cold weather.

eBay seller said hydralic lift was from a 7016h but in fairness the ha home was coated with bedliner and identifiable be shape and build, in the pics. In the pics the hood does not have the slots in the front of the hood. And yes we sectioned the frame to install it in the 912.

Tonite I am going to drain and refill with type F and see what happens. We did note what looks like a film of rust on the fluid that spilled out. I hope that has gotten rinsed out.

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SmilinSam

Are you aware of the little breather on the left side of the transmission? If you lift it up you can fill it faster and easier. Also if its stuck it might be why oil came out when you took the cap off the back.

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rickpilgrim

http://s1316.photobucket.com/user/randlyardcare/library/

Seeing the pics didn't show again there's a link to my photobucket, also on there is the snowblower that's on it. That's our old 7117 blower which we reinforced for commercial use. Doing that added about 40 lbs to it but saved several hrs of welding every few uses and this round I put in a different auger and new bearings and fresh paint. The dexron and new WIX 51086 filter made no difference in any respect at all. I suspect weak charge pump so that's next, providing I can't get a hold of the CL seller with the 90's Sovereign for 5 bills

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JoggerFogger

I'm a little confused.

In the picture (I posted for you) is fluid coming out of the transmission final drive case. You're talking about an added hydro lift for the snow blower and the hydrostatic transmission.

Correct me if I'm wrong, but aren't these 3 different systems, with 3 separate fluids? The hydraulic systems (hydro lift and hydro drive) take red stuff (ATF) and the final drive case takes something like gear oil (80W).

Does the hydraulic lift you added run off the hydrostatic transmission? Sorry if I'm not familiar with this tractor, but it sounds like it's a modified custom jobby anyway.

-Kevin

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GregB

On the FDT Hydro lift, BGB, and Trans(vickers) have different reservoirs. Pretty sure self contained Hydro lift uses 30wt oil. BGB uses 80/90 wt oil? Trans fluid for trans pump.

On the RBT's like above, the final drive gearbox, hydro pump, and the hydro lift use the same Dexron equal, in a shared reservoir. The BGB uses gear oil 80/90 wt?

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rickpilgrim

UPDATE- had the old mech from the Simplicity dealer stop by and am taking his advise. He said the AC 912 was a budget large frame tractor, and only have electric lift/ not hydraulic lift. He says the 912 does not have the charge pump capacity or the internal valves needed to run the lift as delivered and although it could be converted to do this by the time a new charge pump and all the relief valves added figure about $8-900 bucks in parts and a good hour in time would be needed just to get the lift working.

He also said that AW32 would work ok, dexron was preferred for its high detergent property and low tempature flowability.

We checked the vent at it was open, he ran the 912 around the shop yard a few min and when done said do not put any money is this hydro unless you are rebuilding it as it is weak and needs r&r.

I took this as gospel and am getting the 7116 hydro that the powerlift is from. I know it works from the video I saw on it and should be the cure.

Thanks to everyone who helped on this

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Brettw

I am not arguing with a Sim mechanic, but I have to admit this is the first I have heard of a lesser Sundstrand pump in any of the AC/Sim/Acgo, etc. tractors because of engine size or model number. I have never heard of a charge pump being smaller on the 12 horse models?

I'm not saying I know better than the mechanic, I am asking so as to better educate myself. I am also aware that mechanics are not necessarily always correct, so I am hoping someone here can clarify.

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ardisam

Brett, I agree with you. I believe that charge pumps are the same on all the tractors. They just don't have the extra internal parts to have a hydro lift. You can get the extra parts to make it happen. Now, this leads me to a question, does this 912 have the welded so called bushing next the lift quadrant? If not, it's only to have the electric lift or the manual lift.

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cityboy2977

Rick, did you get ALL the parts needed to convert to hydro lift ?

in this thread, Hubbard posted a very good pic for me. made it so easy my wife could have installed them.

http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=133923

i ran into the same problem of fluid being pushed back out of the fill tube. this was because i didnt lift the lil air breather. ive found that filling while running and lifting the breather for a few seconds eliminates ALL air in the lines.

i dont know much about the innards of the hydro units but wouldnt they all have been built on the same assembly line with the same parts ? same models that is.

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Burntime

I know the pumps are the same 700 series, 900 series, 7000 series, 7100 series. The only difference is the shims and plumbing for hydro lift on the 900 and 7100's. You can buy the parts to convert and the shims for under 300 bucks. It just ups the pressure. Look at Rods post. Memory (although not always correct) was the relief is set up from 250 to 750. Yes the 912 was a budget, but its the same pump, same capacity.

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HubbardRA

The 700/7000 series tractors did not come with hydraulic lifts. Because of this, they do not have the second check valve unit needed for the hydraulic lift. The tranny should only run on a hydraulic pressure that is less than 250 psi. The hydraulic lift uses a pressure that is slightly less than 800 psi. If the pressure bypass valve that is used for the transmission is shimmed up to near the 800 psi level,without installing the second bypass valve, it will cook the transmission which cannot withstand those high pressures.The tranny must have both checkvalves installed as shown in the drawing below that I made several years ago to show what I changed when I installed a hydrolift on my AC716H.

ValveWriteup.jpg

ValveWriteup.jpg.2bf3075ce6b797c57c1d69411dbc711d.jpg

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BLT

According to parts book TP400-843, there were six versions of the Sunstrand ident by a 4 digit Sunstrand number on the pump housing before and after part numbers identified by tractor S/N.

However the charging pump number never changed, that being 1685128 for the whole kit. Somewhere in that same time period, late seventies maybe, it was settled on one main unit, 1671582 until the Soverign was retired.

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rickpilgrim

On the charge pump thing is it possible that the early(pre '79) had different charge pumps and that's what my retired mech was talking about? We had tried several shims and valves (toro GM 52 spare transaxle parts, same hydro) with no results but that may have been bad hydro at that point. I bought the matching hydro that the lift came from and other than converting to remote filter and different spec tag it looks identical to what was but works properly.

I was dealing with an unknown condition hydro and from that point of view my retired mechs advise was sound no matter how he expressed it I got his point loud and clear IE get a different hydro from a lift equipped tractor and don't waste money on the 912 one. I can almost bet that's what the dealer would do had I dropped it off by them.

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BLT

Which brings to mind about the charging pump. Are you sure it is installed the correct way. It is easy easy to install it wrong and the you get zip,zilch and nothing. Been there a few times and it is easy to do. And most times there is no scribe or punch refence mark to help you out.

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CarlH

It would also be possible that the various hydro's had different charge pumps from the factory depending on spec number but only a single charge pump kit was offered for replacement purposes.

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HubbardRA

My AC716 is a 1977. That unit will accept a hydrolift from the later 7100/900 series tractors and it works very well. I am using a lift valve from a PowerMax, a lift cylinder from a Sunstar, and the checkvalves listed in the picture above, which I drew after finishing my install.

If you remove the plug from the side of the tranny and find that there are none of the pieces shown above, then the the hydrolift will not produce any lifting force. I could hold my rockershaft with my foot before I installed the correct check valve parts. Now it has enough power to completely push my foot out of the way and not even notice it.

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