gh 718d final drive, no forward or reverse

[nymariner1]

Hello to all,
Make Model: Grass Hopper 52" cut Model 718D, Serial 291101
Questions:
1) I am new to this forum and don't see many 'new' threads. Is this forum is still active?

2) Can someone tell me what the year and make/model of my hydraulic pump and final drive is?

Problem:
There is 'very little' forward or reverse motion to the left drive wheel. I jacked the mower off the ground and started engine. The right wheel spins forward and reverse as normal, the left wheel just rotates slowly in forward and reverse with little power or speed.

History:
The final drive in question had been leaking hydraulic fluid (Would empty the reservoir in an hour of mowing). I would carry fluid with me and add when stopped moving to get back to the garage. IE: Ran low/empty a few times.
The leak was found to be caused by breached gaskets in the final drive casing pieces.
I disassembled the final drive, installed new gaskets and reassembled, with new filter and fluid.
The leak stopped, but now have new 'problem' (see above).

Diagnostics, so far:
I am in NY. I called a GH dealer whom would actually talk to me, in Florida, and the mechanic told me to jack the unit and let run until fluid bled air from the drive. This did not help.
He then said the pump must be failing. He told me the pump must be failing and to start with taking the 'top' off the pump and look for damage??? I took the 5 bolts out and lifted the top housing (containing filter) off. All I see is the parking brake lever hovering over a couple of small stainless steel BBs sized balls in a seat. If I spin the tire, I can see these balls moving up and down, depending on which way I spin the tire. I also see the pump cooling fan attempting to turn, IE: Nudging.

Questions:
3) Is it possible to reassemble the drive improperly? IE: can parts go back together in the wrong order or position and still be able to bolt together the housing? I was working off a blowout diagram that was not 100% clear. The kind Florida dealer faxed it to me.

4) Could running the pump without fluid damage the pump? Where would I find this damage?

Seems TOO coincidental that just after I worked on the drive, the pump fails?? I had been just adding fluid for quite some time and drive always worked well, after adding the fluid...

I await your comments/help/experiences...
Thanks,
Larry

 

[Carscw]

Post the mower model number please.

 

[nymariner1]

Yes, Thank you.
I had already gone back and edited my post to include the model and serial #s.
I put them on second line of my post. Should I have posted them somewhere else?
Thanks,
Larry

 

[bertsmobile1]

Running a hydro with low oil will do damage to the pump & motor so it might be a "stitch in time" , just too late.
When you had it off the ground did you open the bypass valve ?
Generally you open the bypass valve a little then do forward & reverse runs for about 30 to 60 seconds a dozen or so times.
Some times it can take a very long time to bleed the system.
Both the pump & engine are basically a bunch of small pistons ( the bb sized balls ) running on a face cam which either makes then go up & down ( pump ) or they make the face cam go round ( motor).
Very simple but running at very tight tolerances so easily damaged if allow to run too hot ( low oil level ) .

 

[nymariner1]

Thank you Bert for both, a quick reply and for your insights.
I see this forum IS still active. Great!

Yes, I failed the "Stitch in Time" rule. ... IE: "Never enough time to do things right,
...always enough time to do things twice!"


I DEFINATELY ran the mower low and even empty of fluid, several times. However, always seemed to perform well after adding new fluid. Until I worked on repairing the final drive gaskets.

I did lift and run the pumps in forward and reverse many times. I even put the drive in forward and walked away for an hour or so with it running, with no change. "30 - 60 seconds forward and reverse, dozens of times?" No so sure about that, it was last year that I worked on it last. Just getting back to this project now..

To bleed, I was not instructed to loosen a bypass valve as well. At this juncture, it would not be a problem to re-affix the pump top cover and perform this procedure.
Where is the by-pass valve located? All I see are two hydo lines (1" diameter, or so). One feeding the pump and the other returning to the reservoir. No in-line valves connected between them. Also, The final drive is bolted directly to the hydro pump, so, no lines to have a bypass valve installed.

Is there a port available to check/confirm the pump pressure?

Thanks,
Larry

 

[nymariner1]

Additional thought...
Would applying the parking break (Pushes a lever down on both BB's inside the top of the pump, seating them) bypass or simply lock the hydraulic system?

 

[nymariner1]

Hello Again,
Today I jack left wheel, started motor and ran forward and reverse alternately for a minute or two each direction for a half hour,
Wheel spins very fast in both direction, but NO power. I can stop the wheel with my foot...
When I drop the mower on ground, the right drive WAY over powers the left drive. The right drive is smooth , powerful and quiet, The left drive is smooth, no power and make a struggling whining sound.
Any ideas?
Thanks,
Larry

 

[Carscw]

What type of fluid/oil did you put in it?

 

[nymariner1]

Not sure. It was a year ago, but I do know I bought fluid with the same awg numbers that Grass Hopper recommended. There seems to be no issues with the other pump and drive, using same fluid.

Is there anyway to test the hydro pump output? A test port, perhaps? Do you know the make of the pump that this unit came with?

Thanks,
Larry

 

[nymariner1]

Well, thanks to those whom responded!
I can see this is not a very active forum or, nobody has 718D experience here? I will seek help elsewhere..
Thanks again
Larry