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Herky - Jerky Hydraulics

Discussion in 'Mechanic and Repair' started by jim dailey, May 6, 2004.

  1. jim dailey

    jim dailey LawnSite Senior Member
    Posts: 614

    I have a used GDSS w/ 18 hp Kohler. The hydraulics are all over the place. I have adjusted the levers for neutral. The tank is full. The Filter is new. The system has been bled. At full throttle, running along in a straight line is next to impossible. All of a sudden one side or the other will want to grab and throw you off course. There is no such thing as a straight line with this machine. I have to turn the throttle down (there goes blade speed) and constantly play with the sticks to TRY and stay straight. This is my 1st hydro. Should I replace the fluid? Some of it is old. If I change the filter, again, replace the fluid and re-bleed the system, do you think my chances are pretty good at getting somewhere with this? I just hope that I am not looking at new hydro pumps. That can be quite expensive, so I am told. I would appreciate any and all info that anyone is willing to offer. I have the owner's manual and have read it front to back. Thanks in advance to any info that you are willing to share.
  2. fixer67

    fixer67 LawnSite Silver Member
    Posts: 2,100

    We had that problem on a Ferris last year. Our problem turned out to be bad linkage. Each point in the linkage that contected to another link adds to the the total play in the linkage. Check each and ever link from the handle to the pump in vlave shaft. Try this, hold the valve shaft and have some one real slow like move the handle and see how far the handle moves before the valve control shaft does. You May be surprised. On the Ferris even after we put new linkage on it Ferris sent us a set of small shocks (Gas Springs) to help control the hopping. Good Luck
  3. jim dailey

    jim dailey LawnSite Senior Member
    Posts: 614

    Fixer67...thanks for the advice. I will play with that idea this weekend. Hopefully, that will get me somewhere. Thanks again, and I will let you know how I made-out...JIM.
  4. xcopterdoc

    xcopterdoc LawnSite Senior Member
    Posts: 752

    The gas shocks will make a difference. They dampen the control movements and also add some artificial feel to the controls. This in turn will keep you from getting jerky movements and also from spiking the pressures to the drive motors.
  5. metro-hp_48

    metro-hp_48 LawnSite Senior Member
    from TN
    Posts: 874

    If you ever want to get an idea of what it might cost to replace certain items, you can look here (this was the closest to a SS I could find, so I don't know how diff. yours would be, but you might can get a ballpark figure)


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