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Plow Raises Slowly

Discussion in 'Commercial Snow Removal' started by DOD, Dec 8, 2003.

  1. DOD

    DOD Junior Member
    Messages: 17

    I have an 86 GMC with a Fisher Plow. When cold, it works fine, however, after used for a while, I have to rev the engine significantly to get the plow to raise or angle, most often have to back away from the snow also. Is there a fix for this?
  2. Brian Simmons

    Brian Simmons PlowSite.com - Sponsor
    Messages: 196

    It sounds like your pump is worn out. When the plow is cold it will work well but once the fluid warms up it loses its viscosity and the fluid slips between the gears. Take a look at the pump shaft. Is there any scoring at the top? If there is it is a bad ground. Bad grounds will destroy a pump fast as the electric motor seeks ground down thru the pump shaft.
  3. DOD

    DOD Junior Member
    Messages: 17

    It doesn't have an electric motor. It is a total hydraulic system. I have a pump (tranny fluid) under the hood driven by a belt, and a valve body mounted on the inner fender. This is an older system. It works great except for this problem.
  4. hbrady

    hbrady Senior Member
    Messages: 217

    Not to be wise because I'm sure you did this but have you topped of the Hydraulic fluid. Our old Fisher used to spray hydraulic fluid all over the place (good for the lawn :D ) and if I didn't top off the fluid occasionally the action on the plow would be very slow. Just a thought (or a shot in the dark) :drinkup:
  5. DOD

    DOD Junior Member
    Messages: 17

    Not being wise at all, sometimes the simple things are overlooked. Yes the fluid is full, belt tight,etc. I am thinking about looking into the valve body that controls the up/down/angle. Has anyone rebuilt one of these? Is there anything in particular to watch for, etc?
    Last edited: Dec 9, 2003
  6. GesnerLawn

    GesnerLawn Senior Member
    Messages: 127

    DOD - It sounds like you have an old Fisher Speedcast plow. I have the same unit on my 85 Chevy and it is slow too.

    The problem may not be with the pump. Since the pump is driven by the truck engine, it will work faster when the truck is cold and idling higher due to the choke.

    What I do is turn my idle up a little in the winter to speed the plow up. You don't want to turn it up too much though or you''ll be on the brakes all the time, stressing the transmission and running into things.
  7. DOD

    DOD Junior Member
    Messages: 17

    It isn't the RPM due to choke, there isn't a choke hooked up. It has a rebuilt 350 (non stock) with a Holley 650, never could get the choke working properly, so it isn't even hooked up. It definately has to do with temp increasing, but not sure why or where to start looking.
  8. GesnerLawn

    GesnerLawn Senior Member
    Messages: 127

    But increasing the RPMs will still speed up the plow.
  9. DOD

    DOD Junior Member
    Messages: 17

    Yes it will. I talked with someone today (an older guy at a Fisher dealer, you know the one, the one everyone else goes to when they don't know what to do next) and he said it is a weak pump and the only thing to do is to replace it, it can't be rebuilt.

    An interesting note: I can get a New Fisher unit for 197.00 from the dealer, an aftermarket rebuilt unit will cost me 220.00 from the parts store. One of those times it is cheaper to go with the orig manufacturer.
  10. ksland

    ksland Senior Member
    from ma
    Messages: 420

    I just had the same problem, got slower and slower to the point where it wouldn't even raise even at 4000 rpms. Replaced the pump now it lifts fine. Does the plow stay up when you center the joystick and not drop down slowly? If so its the pump. I paid $220 from a Fisher dealer for mine.