# please help with great dane walk behind prob



## betdy1345 (May 28, 2012)

The company I work for is a small outfit i have been with for a while. We have 2 yellow great dane walk behinds with drive issues. I have been tasked with finding a solution. Model ODWZ16BV with hydrostatic drive on a 52 inch mower deck. One of them the left side drive barely moves in reverse. We have tried to adjust the linkage a few times not really making any difference. The other is starting to get squirely like the rate of drive doesn't keep up with the movement of the drive handles and gets really jumpy if you don't have alot of expirience with this type of mower. If anyone has any ideas before I start taking things apart I would be .

Thank you for your time.
Tom


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## paulr44 (Oct 14, 2008)

Not familiar with GD hydro control brackets, so I'll tell you what I can.

Check to ensure the linkage is not only moving the bracket on the pump control shaft, but that the shaft is moving a corresponding amount. Sometimes the brackets become loose or worn and while they move a lot from linkage control, the shaft isn't turning the same amount. If forward direction works fine, it's *probably* in the linkage/control.

Google doesn't return anything on ODWZ16BV. If this is a stand-on unit, the proper way to adjust the linkage is to keep adjusting the linkage "tighter" until when pulling a steering lever backwards it can't reach the handle bar, THEN back off on that adjustment 1 turn of the swivel, re-check and repeat until you can pull the lever back till it hits the stop bar WITHOUT forcing it, you should be done.

It's common for steering arm pivots, linkage connections (rod ends, swivels, bell cranks) to wear. If all those are good, an adjustment should clear it up.

It's unlikely, but not out of the question, that the hydro or wheel motor is NFG.

The only way to properly test a hydro is with a pressure/flow tester, which costs a dealer (not retail) about $450. We have 2, and use them a lot.

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As for the jumpy unit - if this is a sit-down unit in particular, "jumpy" or "touchy" hydro control is usually a result of a bad damper. It looks like a nitrogen gas-shock that holds up your car trunk or hood, but isn't quite one of them. It's a damper, the name describes what it does.

As for rate of movement, or lack of speed, probably linkage.

SIMPLE HYDRO/DRIVE TEST: with the engine at speed, on a gravel or dirt surface, drive the unit up to a wall (not into), edge the front wheels against the wall, then try to run the wall down. The rear wheels should dig holes. Don't sit there abusing the unit trying to see how deep you can go, just a few seconds should indicate if there's good power to the wheels.


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## betdy1345 (May 28, 2012)

These machines are walk behind with a stand on sled lowered to turf when needed. The linkage on them is lever to pump with no dampener by design. There is really only 3 link points on each lever which are ok. The rod to rod link points are a bit worn but don't make a difference. What would the signs be of a pump going NFG? It almost seems like the shaft or something in the pump is temporarily sticking as a change in direction is made which is what makes it jumpy if you don't know how to drive a zero turn.


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## paulr44 (Oct 14, 2008)

The problem you describe is unusual, but not unheard of. If you've eliminated the linkage (again, I ask you physically watch the control shaft the linkage acts upon to ensure it turns a corresponding amount as that is THE USUAL reason for what you're describing) as a problem, then without the luxury of a test kit you'll have to dismantle the pump and do a physical inspection. ALSO, check both hoses well for that side - if there's a leak, it could be sucking air when you attempt to move it in reverse.

You could have Parker or Hydro-Gear pumps. *I am posting some HG service manual excerpts that may help*. A guess would be a charge pump or check valve issue. A rebuild kit will run you anywhere from $30 to $65 on average depending on the brand and model.

A local dealer with hydro experience should be able to help you. We get 1/2 hr. per side to diagnose (using the press/volume test kit), which is typical factory flat rate and fair. THE HYDRO HAS TO BE in the unit to test - you have to run the engine and connect the tester to the hydro hoses.

Look - HG posts their manuals for free! 
http://www.hydro-gear.com/Main/service/service-repair-manuals


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## paulr44 (Oct 14, 2008)

Pics didn't attach...apparently I had to delete older post attachments as I "exceeded" my allotment!


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## betdy1345 (May 28, 2012)

*that's a new one*

This is the 1st time I've heard of a unit sucking air. I will have to look at that. 

It always pays to have multiple views. I thank you for yours. I learn something every time I'm on this website.


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## paulr44 (Oct 14, 2008)

betdy1345 said:


> This is the 1st time I've heard of a unit sucking air. I will have to look at that.
> 
> It always pays to have multiple views. I thank you for yours. I learn something every time I'm on this website.


Yes, have seen that and mind you without a leak present. Was on a new unit no less.


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