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Hydrostatic Transmission Problem


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#1 curtz OFFLINE  

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Posted April 16, 2018 - 07:17 PM

I posted some information regarding a problem with my MTD 995 transaxle not working on the MTD forum page but thought that it may help to expand the request for help on the full forum.  I hope I am not being repetitive but have a couple of questions regarding this issue.  The tractor won't move forward or reverse and I thought it may be the hydraulic valve the controls the deck and pto lift and routes the transmission oil from the pump back to the transaxle.  I pulled the valve and cleaned it and installed new o-rings on the hope that it would fix the problem but no luck. I changed the oil filter and oil and no luck.  I have had this problem happen in the past where the drive quit working and all I had to do was work the hydraulic lift control back and forth a couple of times and the drive started working.  The cost to replace the hydraulic lift control valve runs around $400 so I am looking at different options. First question is can I just connect the oil supply feed hose from the pump to the valve to the hose that connects the valve to the transaxle. I feel as though there should be some restriction and control in the oil flow from the pump to the transaxle so I don't want to try this unless someone else can let me know if this has been done in the past without causing damage to the transaxle.  I don't need the hydraulic lift anymore as I only use the tractor to operate a Johnson front end loader that I installed a couple months back. The loader has its own hydraulic pump.  Next I thought about putting a t in the line between the pump and the transaxle with a pressure gauge and manual valve to control the flow.  Is this a good idea or not?  

 

Anyone who has ideas, comments or recommendation can feel free to share and I would greatly appreciate all of your input.

Thanks.

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#2 boyscout862 OFFLINE  

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Posted April 16, 2018 - 07:34 PM

It does sound like you need to bleed it or you may have a hose that is collapsing. Good Luck, Rick


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#3 curtz OFFLINE  

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Posted April 16, 2018 - 07:44 PM

Thanks Rick. Do you recommend loosing a fitting at the control valve to bleed it or at the transaxle?
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#4 olcowhand ONLINE  

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Posted April 16, 2018 - 08:04 PM

You do not need any restriction if you remove the hydraulic spools entirely.  When you are not using the hydraulic levers, the oil free-flows right back to the hydro system.  Just make it a loop circuit if you take out the valves.  I have never been inside an Eaton hydro, so I can't help you with your problem.


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#5 glgrumpy OFFLINE  

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Posted April 16, 2018 - 08:19 PM

I'm betting some kind of operating linkage problem, pin out, or something easy. Rarely do the drives quit working. I have similar tractor, but have not had apart to see links or been under. Find manual, maybe on here, and look over the adjustments of these systems first before tearing stuff off. Many times with all these links, just a good greasing, cleaning and lubing of them makes them move again and work correctly.


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#6 Sawdust ONLINE  

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Posted April 16, 2018 - 09:16 PM

Not familiar with yours but do you have a free wheeling valve hid anywhere or linkages needing adjusted. Keep us posted

Edited by Sawdust, April 16, 2018 - 09:16 PM.

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#7 glgrumpy OFFLINE  

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Posted April 17, 2018 - 03:19 AM

Just thought, check your axle range lever. Sometimes they get bumped out of engagement into nuetral. Again, they need oil on links to keep easy going.
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#8 curtz OFFLINE  

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Posted April 17, 2018 - 08:34 AM

Thanks everyone for your responses. I have checked all the linkage parts and can see that everything is connected and moving smoothly from the hand lever to the plate that moves the round control part on the transaxle. Not sure if there are any air lock issues but everything was working when I parked it. I have changed oil and the filter yesterday so I will check for any air lock problems now. I think I will bypass the control valve and connect the hydro line from the pump to the line that feeds oil to the transaxle and see if that gets it going. I will follow up with an update as soon as I get this done. I no longer need the hydraulic lift control for the 3 point or deck as I only need the tractor for the front end loader and the loader has it’s own hydro pump that runs off the front pto.
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#9 chieffan ONLINE  

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Posted April 17, 2018 - 08:46 AM

As olcowhand said, when not being used the oil free flows straight through the lift control valve.  Removing it would not gain anything but extra work.  If this started after you changed the oil and filter it could very easily be air in the system. Raise the rear wheels off the ground so their is little resistance to them rotating and work the direction lever back and forth to try and get the air out of the system.   Good luck.


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#10 curtz OFFLINE  

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Posted April 17, 2018 - 02:11 PM

I bypassed the hydraulic valve and there is no oil pressure from the pump. I loosened up the oil filter and no oil at that point so I removed the line at the pressure side of the pump and tried to pump a little oil down into the pump to see if it would prime but No luck. I am thinking that the pump has failed and will need to be replaced. Any other ideas. I did jack up the tractor and worked the hand control back and forth with the wheels off the ground but no oil pressure anywhere after the pump. I checked and there is plenty of oil in the pump.

#11 KennyP OFFLINE  

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Posted April 18, 2018 - 07:12 AM

Sounds like a charge pump issue to me. Haven't messed with one of these.


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#12 curtz OFFLINE  

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Posted April 18, 2018 - 10:15 AM

​I did change oil in the transaxle and replace the filter but one thing that I still question is if the unit is air locked.  First off I did use straight 30 weight oil as I couldn't find 20 weight oil so is there a chance that this is to heavy and causing some air lock issues. Secondly in the manual it says to bleed air from the vent.  Where is the vent?  I will pull the tunnel cover to see if I can spot it on top of the transaxle? I did jack up the tractor and tried moving the hand control lever back and forth at different engine speeds and no luck. I too am beginning to believe the charge pump failed but it seems a bit unlikely especially if there is a possibility that the thing is just air locked. 



#13 olcowhand ONLINE  

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Posted April 18, 2018 - 11:58 AM

  30wt will work fine in those, so that isn't the issue.  Either it has an air lock, or the charge pump has failed.  The hydro won't pull the tractor if the charge pump isn't pumping, so your hydrostat main unit may be fine and just in need of charge pump repair/replace.


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#14 limebuzz OFFLINE  

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Posted April 18, 2018 - 07:43 PM

Could be your driveshaft coupler at the hydro pump. Key sheared off?
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#15 curtz OFFLINE  

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Posted April 19, 2018 - 08:58 AM

I will take a closer look at the driveshaft but I believe it is turning the pump.  I have tried a couple of time to bleed out the air and no luck so I am inclined to believe that it is the charge pump.  Does anyone know if there is a kit for the charge pump available.  The cost to replace the charge pump is more then what the tractor is worth.






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