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Discussion Starter #1
My 797 has a little over 1000 hrs on it. I had been mowing fine today when suddenly the right wheel would not drive.

Pulling the right handle back gives no result, pushing it forward gives a shuddering sound but no motion.
Left side work as normal.

with engine off and park brake off I can roll machine forward by hand. The right side will roll backward by hand but the
left side will not roll backward.

I can see no leaks, none in the grass and none on the trailer.

I have not got it in the air yet, took awhile to get it back on the trailer and off the trailer back at home.

ANy ideas what the problem could be other than obvious things I may see after I pull a wheel tomorrow and look around?
 

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Chief Stick-picker-upper
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Welcome to GTT.

Just a thought. Check to see if one of the bypass(free-wheeling) valves backed out.

tca13896-john-deere-hydro-pump-777-797-tca13896-drive-nib.jpg

Using the Free-Wheeling Pump Release Valves


NOTE: The free-wheeling pump release valves must be turned fully clockwise (closed) during normal vehicle operation.
When the machine needs to be moved without starting the engine, use the free-wheeling pump release valves:
1. Lock the park brake.
2. Lift and secure operator seat platform in the raised position.

3. Loosen the jam nut on each free-wheeling valve using a 17 mm wrench. Use an 8 mm wrench to turn both free-wheeling pump release valves (A) counterclockwise approximately 1/4 turn.
4. Lower seat.
5. Unlock park brake.
6. Push machine to desired location. Due to hydraulic system drag, machine will move slowly.
IMPORTANT: Avoid damage! The free-wheeling valves can be damaged if overtightened. Use care not to overtighten.


7. To return to service, tighten both free-wheeling valves to 6.9 N·m (61 lb-in.). Tighten jam nuts to 19.6 N·m (173 lbin.).
 

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flyweight, Is that one unit (motor/pump) for both wheels?
 

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Discussion Starter #4
I adjusted both the release valves but there was no improvement.

With the mower lifted, the right side wheel can be rotated by hand in both directions,
the left side will rotate forward but not reverse. Park brake off, engine off.

I have around 1200 hrs, I maintain it myself as I am a mechanic.
I failed to write down the hours of the last hydraulic filter change, it was 2014 and I put at most 100 hrs a year so I should be OK there.

I did get lax this summer on cleaning the mower, often just a quick
blow off with compressed air. Last week I power washed it thoroughly but can't see where
that would have caused any problems with the drive system since I have done it numerous times thru the years.
 

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Discussion Starter #6
I have the service manual, always have one for equipment I own.
(except for the Simplicity Sunstar I can't find)

It does not help with diagnostics of one side not working.
 
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Chief Stick-picker-upper
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flyweight, Is that one unit (motor/pump) for both wheels?
Dual pump, sharing the same housing.

I adjusted both the release valves but there was no improvement.

With the mower lifted, the right side wheel can be rotated by hand in both directions,
the left side will rotate forward but not reverse. Park brake off, engine off.


I have around 1200 hrs, I maintain it myself as I am a mechanic.
I failed to write down the hours of the last hydraulic filter change, it was 2014 and I put at most 100 hrs a year so I should be OK there.

I did get lax this summer on cleaning the mower, often just a quick
blow off with compressed air. Last week I power washed it thoroughly but can't see where
that would have caused any problems with the drive system since I have done it numerous times thru the years.
I'd have to think the problem is in the Pump(s) itself. A wheels should not be able to be turned by hand if the pump is in good working order.
 
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Discussion Starter #8
I sent an Email to zeroturnman.com.
He answered my email twice even on a SUnday.
He knew right away it was a broken shaft that caused debris to take out one side of the pump.

When I took the wheel motor apart, the shaft was broken and there was debris in the fluid.
He supplied info on using gun cleaning equipment and a cable to clean the lines with kerosene
and disassembling the other wheel motor to clean it.

Basically the entire system needs to be cleaned out and the right wheel motor and entire pump replaced.
I have not taken the pump apart, but I bet it looks like the bad pump in his video.

He provided this help before I ordered any parts from him, let's hope the parts ordering goes as well.

Thanks GTT forum.
 

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Technova, glad to hear you're on the right path to repair. :thumbup1gif:
 

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Discussion Starter #10
Lotsa cash will fix it. I plan to replace the other wheel motor rather than risk a problem, it has 1200 hours on I anyway.
This is my personal mower for my property, so it hurts a little since it won't make me any money back.
 

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Lotsa cash will fix it. I plan to replace the other wheel motor rather than risk a problem, it has 1200 hours on I anyway.
This is my personal mower for my property, so it hurts a little since it won't make me any money back.
Yeah it is never fun to have big ticket repairs but if the machine is otherwise mechanically sound it is like getting a "new" machine for a lot less than a new machine. In this sense Zero Turns are pretty basic. An engine, a PTO clutch and a couple hydrostatic drive units. Not much else to them. As long as the deck is in good shape and the engine running strong, it is likely worth fixing. It just may not have been in the budget which causes that sting.

Any idea what caused the shaft to break? Did you hit something? Maybe going at high speed, hit a bump and a dive wheel came off the ground as you were trying to turn or stop so when it came back down it snapped the shaft? I am not sure which shaft it is that broke but I can normally see bearings letting go with age than a shaft just breaking unless there was some form of impact or stress. That is unless the part was built too weak for the application. Then it could have broken at 10 hrs or 2000. While it might make sense to do preventative maint and replace the shaft, if the new one is equally susceptible to just breaking, I don't know that I would bother. If they are known to be weak and the replacement is stronger, then I would go for doing both. If they are the same and it was a freak situational thing that broke it, then I would skip it. Just fix it and get back to mowing. As I said it is one thing to say I have to crack open the case anyhow, I might as well replace all the seals and bearings on both sides but I don't know that this sounds like the point of failure.

To me it sounds like you are doing your filter and fluid changes so it isn't likely just an abuse or lack of PM case.
 
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Discussion Starter #12
I had been locked out of here for awhile, complicated password system for a forum!

I replaced both wheel motors from zeroturnman and bought a pump online with a reference from zeroturnman.
I cleaned the lines, reassembled and all is working fine, it is put away for the winter.

I do not know what caused the problem, I have two rural properties and mow them hard. I bought a quality mower
and I use it. Now, I don't intentionally abuse it but I do run it fast. I know where the bad bumps are and slow or avoid them.
I need new tires and got stuck a few weeks before the problem and may have damaged it in trying to rock it. I called a friend to help with his 4 wheeler and he pulled it before I got back there. 10-15 yds without the bypass released, may be the problem.
I had used it at home after that and saw no problem. The next time I took it to my property, It felt sluggish on the RS. I stopped and checked the tire, felt like flat.
It was not flat and I could find no other problem. I continued on and it stopped an hour later. Looking back, the shaft was broken but still worked, as I used it it ground the two ends of the shaft until they would slip and motion stopped.
HAd I realized what was happening and stopped when it felt sluggish on the RS, I may have saved the pump.
Experience is the best , although expensive, teacher. Now I understand how the entire hydro system works.
The deck is great, motor runs great, clutch new 2 years ago, and hydro is all new so I should have some good years of service left.
 

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Had I realized what was happening and stopped when it felt sluggish on the RS, I may have saved the pump.
Experience is the best , although expensive, teacher. Now I understand how the entire hydro system works.
Experience is something you get right after you need it!
 
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I've notice...last years mowing, that my right drive motor is "some-what" harsh ( more effort) to make a left turn operation by using the right lever. There no noise as such to make me think it is the gear motor that needs looking at. It could be just a adjustment is needed.
 
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