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Hey Guys,
I really need some help here. I'll start by saying I respect you guys and your knowledge on here & appreciate any help I can get. This is my first post, I'm normally good with Mechanical Stuff as I worked for years as an ASE Master Technician in Various Dealerships, I will try to help others as I can but I'm dealing with something I've never had to deal with before.
I ran a Lawn Care Business for years using Grasshopper & Gravely Mowers but recently sold my business. I never had to replace any Hydro. Pumps/Wheel Motors, Etc. Everything Else but not any Pumps as I was lucky in all of those years.

I currently have a little Troy Bilt Mustang RZT 50" w/ 22 HP Kohler and it's done a great job on my personal yard & a few neighbors I do just to be nice. It has about 300 hours on the clock & is as good as New other than one issue.
I'm afraid one of my biggest fears is coming true. Here's the deal: I start up my Mower & Mow for approximately 30-40 Minutes Max & my Left Wheel Gradually loses Power until it slows to a crawl. If I cut it off & let it sit for a while & cool off it goes back to normal until it gets hot again. I usually mow half of my yard, weedeat while the mower sits & cools off, then I finish up.
I know the part number for the Left Hydro Pump is 618-04431 and is superseded by 618-04431A, but these are so expensive it's insane especially considering the Mower was not all that expensive to begin with.
I was hoping you guys could point me in the right direction. Is there something I can check or adjust to fix this issue, I doubt it but must ask, I've checked the Linkage that connects the control lever to the Pump that drives the Left Wheel but it seems fine, I only did that because my uncle who owned it before told me he adjusted it once to fix a minor tracking issue, it may have just been this Pump starting to fail. But it's good until it heats up, so can I have any hope of removing & rebuilding it, or is there a source other than EBay & Larger Online Parts Dealers to look for a good, used Pump.
I feel confident in rebuilding it, I used to rebuild Commercial Air Conditioning Compressors that were mounted inside of ThermoKing Mobile Refrigeration Units on Truck's/Trailers & All Kinds of Engines & A Few Transmissions over the years. Is there a Rebuild or Overhaul Kit Available for these Hydro Pumps? If so, would anyone happen to know a place to get one or a part number for a Rebuild kit, I seen a few on EBay- Some with Seals/Gaskets & some with those & a few hard parts like gears & an axle if I'm not mistaken.
I don't know what to do & I'm desperately trying to find some help. Could this possibly be solved any other way, my belt that drives the Pumps Wouldn't be likely to be an issue since the Right Pump is Working Perfect. As far as I can tell, all linkages are properly adjusted. I haven't checked the fluid level in the suspect Pump. I read it's a sealed unit, but I seen a guy in another thread somewhere talking about adding a precise amount of Synthetic 20W-50 Motor Oil to his Pump which seemed odd but I don't doubt anything these days. I just wanted to get some information from some people who really know what's going on with these types of issues regarding my Pump Working as It Should until getting hot, and upon cooling down it goes back to normal until hearing up again- I apologize for rambling on such a long post but I really need help.

I appreciate any responses and/or advice.

If this is a lost cause, I could throw it on Craigslist for $600-$800 or Simply Part It Out Online if it's not worth messing with. I can't help but wonder about the fact that even if I get this straightened out that the Right Side Hydro Pump may go bad at any time as this one has. But I'd really like to fix & keep this Mower if it's at all possible without having to spend a small fortune on it. Please Help Guys & Know that it's Greatly Appreciated! Thanks- Daniel
 

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Tough situation. Since you are mechanically knowledgeable you might try taking it off and changing fluid since you won't be out anything much more than time.
There were a few posts around a few years ago about cub cadets (same setup) having left pump I think going out from water getting in.
Have you power washed or hosed yours off regularly? I think it's best to keep water away from these machines.
Is fan on yours in good shape with all fins?
Do you keep it at full running engine speed all the time to keep it coolest?
It is possible for a belt to slip one side and not the other but I doubt your issue is belt related but it never hurts to test by increasing belt tension temporarily or trying new belt.
They are not terrible to repair /rebuild but part cost gets up there quickly. That's the bummer.
Many people have gotten improved performance and extra life from fresh synthetic oil.
 

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Discussion Starter · #4 ·
I really appreciate your response & the helpful information my friend. To answer your questions- No, I personally haven't been washing it at all, I just keep the deck clean & free of debris/grass, etc. And the belt seems to be tight enough but I'll double check that just in case, it would be great if that or changing fluid would be good enough to fix it. Although it's stayed clean after my using it & it's still very clean and I've mowed with it several times, it's possible that it could've gotten moisture in the wrong place before I bought it. It had 296 hours on it when I bought it, but I swear it looks & runs & does everything else as good as any new Mower I've owned, after about 10 hours of use the Pump started acting up & that's what's led me here. I do mow with the engine at full throttle & my fans are fully intact.
I am going to remove the Left Hydro Pump & Replace The Fluid, it's very possible that it's never been changed, I hope so but have no way of knowing. My uncle bought it from a friend as a favor basically because he needed cash, the guy never bought it back, my uncle didn't like it & bought a new John Deere Riding Mower & offered me this Troy Bilt Mustang RZT 50" for $500, it's a 2013 I do believe & like New still, I will try to fix it myself & may Rebuild the Pump if New Hydro Fluid/Oil Doesn't Help but after seeing what parts bring on EBay I'll sell it complete or may just part it out if nothing else & I'll have to break out the John Deere Rider again, I hope it works out but if not I think I'll get my money back, but I'd much rather have the mower and I'm willing to spend some money on it but not any serious amount- maybe $200-$300 For Rebuild Parts or Possibly a Good, Used Left Hydro Pump.
I read on a forum where a guy had the same issue & installed a new Pump but he didn't fully flush the system of the old fluid & it had tiny metal particles that ruined the new Pump in less than 2 hours, maybe only 1 hour, so I'll disassemble & inspect the Left Hydro Pump for any Worn or Damaged Metal Parts, if I find anything I'll remove the Right Hydro Pump also & flush it & all of the lines to keep anything like that from happening.
Also, I seen several cases where the Hydro Pumps got covered partially with grass, dirt, & other debris & this kept the Pump from cooking properly & overheated then blew a seal inside which led to it needing a Rebuild so I'll have to check the area between the top of the Pumps & Frame as that was the most common spot for the buildup to happen since it's hard to see & commonly missed when cleaning, so if anyone sees this in the future, check that out as it could be an issue and if you're not having that issue be sure to keep the entire Hydro Pump Housing Clean & Free of Dirt/Grass/Debris, Etc. When the Pump overheard the Fluid breaks down into sludge & According to a very respected factory technician on another forum nearly all Pump failures are related to Overheating from the Old Fluid that's broken down & turned into sludge which leads to poor lubrication & Bearing failure, which leads to metal particles damaging the internal seals & ultimately Pump Failure. That sounds very logical to me and just reaffirms the importance of preventative maintenance including servicing your Hydro Pumps Regularly with a High Quality Fluid As Reccomended by the Manufacturer of the Mower/Pump.

I'll let you guys know what happens as soon as I can get to it. I believe I'll mow the yard first in case it ends up taking a few days waiting for parts or something so I don't have to endure the torture of using a slow riding mower.
Thanks again for your help and I appreciate your time you took to respond. I'll be on here & I'll be looking around & trying to help anyone I can!
 

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I really appreciate your response & the helpful information my friend. To answer your questions- No, I personally haven't been washing it at all, I just keep the deck clean & free of debris/grass, etc. And the belt seems to be tight enough but I'll double check that just in case, it would be great if that or changing fluid would be good enough to fix it. Although it's stayed clean after my using it & it's still very clean and I've mowed with it several times, it's possible that it could've gotten moisture in the wrong place before I bought it. It had 296 hours on it when I bought it, but I swear it looks & runs & does everything else as good as any new Mower I've owned, after about 10 hours of use the Pump started acting up & that's what's led me here. I do mow with the engine at full throttle & my fans are fully intact.
I am going to remove the Left Hydro Pump & Replace The Fluid, it's very possible that it's never been changed, I hope so but have no way of knowing. My uncle bought it from a friend as a favor basically because he needed cash, the guy never bought it back, my uncle didn't like it & bought a new John Deere Riding Mower & offered me this Troy Bilt Mustang RZT 50" for $500, it's a 2013 I do believe & like New still, I will try to fix it myself & may Rebuild the Pump if New Hydro Fluid/Oil Doesn't Help but after seeing what parts bring on EBay I'll sell it complete or may just part it out if nothing else & I'll have to break out the John Deere Rider again, I hope it works out but if not I think I'll get my money back, but I'd much rather have the mower and I'm willing to spend some money on it but not any serious amount- maybe $200-$300 For Rebuild Parts or Possibly a Good, Used Left Hydro Pump.
I read on a forum where a guy had the same issue & installed a new Pump but he didn't fully flush the system of the old fluid & it had tiny metal particles that ruined the new Pump in less than 2 hours, maybe only 1 hour, so I'll disassemble & inspect the Left Hydro Pump for any Worn or Damaged Metal Parts, if I find anything I'll remove the Right Hydro Pump also & flush it & all of the lines to keep anything like that from happening.
Also, I seen several cases where the Hydro Pumps got covered partially with grass, dirt, & other debris & this kept the Pump from cooking properly & overheated then blew a seal inside which led to it needing a Rebuild so I'll have to check the area between the top of the Pumps & Frame as that was the most common spot for the buildup to happen since it's hard to see & commonly missed when cleaning, so if anyone sees this in the future, check that out as it could be an issue and if you're not having that issue be sure to keep the entire Hydro Pump Housing Clean & Free of Dirt/Grass/Debris, Etc. When the Pump overheard the Fluid breaks down into sludge & According to a very respected factory technician on another forum nearly all Pump failures are related to Overheating from the Old Fluid that's broken down & turned into sludge which leads to poor lubrication & Bearing failure, which leads to metal particles damaging the internal seals & ultimately Pump Failure. That sounds very logical to me and just reaffirms the importance of preventative maintenance including servicing your Hydro Pumps Regularly with a High Quality Fluid As Reccomended by the Manufacturer of the Mower/Pump.

I'll let you guys know what happens as soon as I can get to it. I believe I'll mow the yard first in case it ends up taking a few days waiting for parts or something so I don't have to endure the torture of using a slow riding mower.
Thanks again for your help and I appreciate your time you took to respond. I'll be on here & I'll be looking around & trying to help anyone I can!

Hi. I'm having the same issue, same side. What ended up happening?
 

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Hey Guys,
I really need some help here. I'll start by saying I respect you guys and your knowledge on here & appreciate any help I can get. This is my first post, I'm normally good with Mechanical Stuff as I worked for years as an ASE Master Technician in Various Dealerships, I will try to help others as I can but I'm dealing with something I've never had to deal with before.
I ran a Lawn Care Business for years using Grasshopper & Gravely Mowers but recently sold my business. I never had to replace any Hydro. Pumps/Wheel Motors, Etc. Everything Else but not any Pumps as I was lucky in all of those years.

I currently have a little Troy Bilt Mustang RZT 50" w/ 22 HP Kohler and it's done a great job on my personal yard & a few neighbors I do just to be nice. It has about 300 hours on the clock & is as good as New other than one issue.
I'm afraid one of my biggest fears is coming true. Here's the deal: I start up my Mower & Mow for approximately 30-40 Minutes Max & my Left Wheel Gradually loses Power until it slows to a crawl. If I cut it off & let it sit for a while & cool off it goes back to normal until it gets hot again. I usually mow half of my yard, weedeat while the mower sits & cools off, then I finish up.
I know the part number for the Left Hydro Pump is 618-04431 and is superseded by 618-04431A, but these are so expensive it's insane especially considering the Mower was not all that expensive to begin with.
I was hoping you guys could point me in the right direction. Is there something I can check or adjust to fix this issue, I doubt it but must ask, I've checked the Linkage that connects the control lever to the Pump that drives the Left Wheel but it seems fine, I only did that because my uncle who owned it before told me he adjusted it once to fix a minor tracking issue, it may have just been this Pump starting to fail. But it's good until it heats up, so can I have any hope of removing & rebuilding it, or is there a source other than EBay & Larger Online Parts Dealers to look for a good, used Pump.
I feel confident in rebuilding it, I used to rebuild Commercial Air Conditioning Compressors that were mounted inside of ThermoKing Mobile Refrigeration Units on Truck's/Trailers & All Kinds of Engines & A Few Transmissions over the years. Is there a Rebuild or Overhaul Kit Available for these Hydro Pumps? If so, would anyone happen to know a place to get one or a part number for a Rebuild kit, I seen a few on EBay- Some with Seals/Gaskets & some with those & a few hard parts like gears & an axle if I'm not mistaken.
I don't know what to do & I'm desperately trying to find some help. Could this possibly be solved any other way, my belt that drives the Pumps Wouldn't be likely to be an issue since the Right Pump is Working Perfect. As far as I can tell, all linkages are properly adjusted. I haven't checked the fluid level in the suspect Pump. I read it's a sealed unit, but I seen a guy in another thread somewhere talking about adding a precise amount of Synthetic 20W-50 Motor Oil to his Pump which seemed odd but I don't doubt anything these days. I just wanted to get some information from some people who really know what's going on with these types of issues regarding my Pump Working as It Should until getting hot, and upon cooling down it goes back to normal until hearing up again- I apologize for rambling on such a long post but I really need help.

I appreciate any responses and/or advice.

If this is a lost cause, I could throw it on Craigslist for $600-$800 or Simply Part It Out Online if it's not worth messing with. I can't help but wonder about the fact that even if I get this straightened out that the Right Side Hydro Pump may go bad at any time as this one has. But I'd really like to fix & keep this Mower if it's at all possible without having to spend a small fortune on it. Please Help Guys & Know that it's Greatly Appreciated! Thanks- Daniel
That’s a hydrogear product and you can go to their site and download service instructions on how to change oil and filter and explains the oil capacity. Good luck. They also have a tech paper on water getting into unit from pressure washing with a kit to prevent water from getting in unit.
 

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forkz
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i have a 06 z force cub cadet it has izt trans also sealed thats not many hours my right side starting acting up after about a 1000 hours did fine till it got hot pulled pan all gears metal parts looked good oil was thin and dirty put in new fluid worked like new
 

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I am having the same problem.i am lost and confused.
Has anyone found out what the final solution was? I’m having the same problem with Troy Bilt Mustang w/ a 25 HP Koehler, right side hydro. It starts leaking when it gets hot. Loses all power. I’m stuck going in circles to the right. I’ve got a really well cut circle in my yard.
 

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That is typical wear of the hydraulic pistons and cylinders of the pumps and motors. When they get hot and the clearances expand, they loose their sealing and hydraulic pressure and will slow down.
Hydro-gear products are well known for that problem and require expensive parts replacement and labor costs.
By using a heavier weight oil, it will only help for a little while, and the problem will continue, thus requiring a rebuild with new parts.
I've rebuilt hundreds upon hundreds of Hydro-gear transmissions because of that. They used low quality parts during manufacture that don't last long at all and need replacement far too soon.
 

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Thanks for the info. Are they sealed or can I add heavier weight oil to it?

I’ll get what I can put of it until it NEEDS replaced.

Are there any manufacturers that make a quality version?
 

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The machines I own, that have hydro-gear pumps, motors and combined units, some from new, and some used, have worked well for me, and some are twenty years old and used commercially. If they were that poorly made, they would not be used throughout the industry, from entry level machines to high-end professional units.

It depends on which specific unit you have, as to how easy it will be to change the oil in it (lower end ones may be made to just be filled at the factory, so they would have to be removed/turned upside down to do it, higher end ones have a proper drain port).
 

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The machines I own, that have hydro-gear pumps, motors and combined units, some from new, and some used, have worked well for me, and some are twenty years old and used commercially. If they were that poorly made, they would not be used throughout the industry, from entry level machines to high-end professional units.

It depends on which specific unit you have, as to how easy it will be to change the oil in it (lower end ones may be made to just be filled at the factory, so they would have to be removed/turned upside down to do it, higher end ones have a proper drain port).
I haven’t seen any other manufacturer of these. Not having competition is not good for quality. Especially in the lower end models.

Thanks for the note.
 

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Tuff Torq also makes them. Hydro-gear are a bit better than the Tuff Torq. Those 2 companies are in competition with each other building the 'Low End' versions.
Those 2 companies build most of them for all the major manufacturers now days due to their low price, especially on 'Home owner' units to help keep costs down and increase profits for the manufacturer. A good majority of their parts are 'Out-sourced' from cheaper suppliers, made with much lower quality materials, mainly all 'Re-cycled' materials to keep costs down.
Years ago companies like Vickers, Eaton, Sundstrand, Rockwell, Dana-Spicer and a few others made the good quality units, but unfortunately they no longer are used in home owner and many commercial products anymore due to their higher price, quality, reliability, and longevity. They were made with U.S. made and sourced parts that were built with high quality and longevity in mind, not 'Throw Away' like everything is made today. They used 'New' 'Virgin' steel products, NOT 'Re-Used'-'Re-Cycled' scrap steel that is used in most all production today.
Those units were 'Over Built' back in their day so they lasted much longer than expected and were not replaced all the time with 'New' like things are made today, so that cut down on sales and profits of 'New' items being sold and cut down on manufacturing demand.
 

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forkz
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i pulled the pan off mine without removing from machine
 

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Really just a bandaid and not a very good one sometime as you have no idea how good a result you will get or how long it will last. i
If you're going to spend all the time to remove the hydro and take it apart you should have least get the internal kit to replace those parts for 100% function or close to it and longer durability.
 

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Just went through this with my CC right hand trans. A bit more than $320 for a rebuild kit was happy. Well, it lasted for about four mowings, maybe twenty hours... and did the same thing. Great when cold, slow when hot. Getting ready to install a new trans. $600 bucks for this. Thought I was better at this stuff...but....
Hopefully it goes in this Sunday.
 

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run the mower until it the left side starts acting up then immediately probe both motors with a infrared temp gun , see any temp differences? ever changed the oil in the hydraulic circuits ? if it's warmer than the other side I would suspect a bearing in the motor. possibly a blockage from debris ? leaking air in the system causing cavitation?
 
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