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How to Repack Lift Arm Ram on Fisher MM1 SEHP straight blade

Discussion in 'Truck & Equipment Repair' started by alohazabel, Jan 10, 2015.

  1. alohazabel

    alohazabel Member
    Messages: 44

    Can someone give me a quick step by step tutorial on repacking the lift arm on my fisher MM1 SEHP straight blade?

    My plow has been leaking slightly from the packing nut since I've owned it, but it seems to be getting a little worse lately. I also noticed the plow is making a new noise the last few days every time I drop it down. Its still functioning OK, but I thought I should try to fix the leak and hopefully get rid of that noise.

    It looks pretty easy, but I just want to make sure I'm not missing anything, get all the parts I need to do it right, etc.

    Thanks
     
  2. alohazabel

    alohazabel Member
    Messages: 44

    packing nut size

    also wondering ...what size is the packing nut on the sehp lift arm?
     
    Last edited: Jan 10, 2015
  3. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,002

    There's seals on the ram, and one wiper seal inside the nut.
     
  4. alohazabel

    alohazabel Member
    Messages: 44

    can I get to everything by unhooking the triangle, loosening the packing nut and pulling the ram?
     
  5. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,002

    Rams gotta come out. How's the ram? Rusty and pitted means replacement
     
  6. alohazabel

    alohazabel Member
    Messages: 44

    some slight pitting, no visible rust... hoping to get about three more years out of the plow, should I replace it?

    how do I get the ram out?
     
    Last edited: Jan 10, 2015
  7. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,002

    If it was mine yes I would.
     
  8. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 8,608

    Have you tried tightening it a little and topping off the hydro fluid

    Unless its gushing out I'd try this first
     
  9. alohazabel

    alohazabel Member
    Messages: 44

    yes. The only wrench I have on hand that would fit it is a big old pipe wrench. I tried to tighten it, but I couldn't budge it with the wrench I have.

    Its not gushing, and the plow is still functional.

    I just wanted to get it taken care of before I have a problem during a snow storm.

    But if repacking it is a huge hassle, I guess I could just keep using it as is for a while
     
  10. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,002

    Actually, removing the nut is about the hardest part
     
  11. alohazabel

    alohazabel Member
    Messages: 44

    Diesel- Tell me if this sounds about right....

    Pull the pin that attaches triangle to lift arm

    Loosen and Remove the packing nut

    then pull the ram up and out of the tube,

    replace the seals and packing, slide it back in

    retighten the packing nut

    and reattach to the triangle

    ????????
     
  12. alohazabel

    alohazabel Member
    Messages: 44

    and I can replace the ram if needed at the same time
     
  13. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,002

    That's about right....how ever I'll.add

    Remove Allen plug on the side of the lift ram housing. That'll drain the fluid in the ram housing.
    Lift up ram with triangle attached still.
    Then loosen the nut.
    Then take off triangle, but before you do, bungee cord the pump "back" or it'll fall forward.
    Take nut all the way off.
    Pull up on the ram.
     
  14. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,002

    Pull the seals off.
    Replace the seals.....I like to use lubriplate on the seals to get them "wet"
    Install seals.
    Push all the way down to the lock ring of the piston.
    Install....May have to use a hammer and a punch to get the seals all the way down in the bore.
    Replace wiper seal in the nut......May have to wire wheel the nut as they rust.....If you really wanna be anal you can order a nut just to be safe.
    Tighten nut....hand tight
    Raise ram. Install triangle....Then tighten nut....Tighten to nut contacts the packing then 1/4 more.
     
  15. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,002

    Since the lift ram is gunna be out, I always flushed the bore out. You wouldn't believe how much crap was in the bottom. Just fyi..
     
  16. alohazabel

    alohazabel Member
    Messages: 44

    Diesel- thanks alot for the detailed step by step. It seems alot clearer to me now.

    I'm going to have to wait until monday to get the seals and then I'll attempt it.

    If I get stuck I'll be back begging for more advice.

    Thanks again
     
  17. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,002

    No bother....
     
  18. alohazabel

    alohazabel Member
    Messages: 44

    stuck packing nut

    Diesel- You weren't kidding about loosening the packingnut being the hardest part of this job.

    I've been giving it doses of PB blaster, working on it with a big pipe wrench, a crescent wrench, a cheater bar, and I can't get it to budge.

    I tried a little heat, but not much yet. I wasn't sure if I should heat the nut or the tube.

    Any advice or tips on how to break it free with out twisting the top off of the packing nut?

    Its not reverse threaded or anything like that is it?
     
  19. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,002

    No it's not reverse threads. Heat just below the nut where it threads into the housing. Be careful tho the housing is aluminum, so light heat and keep the torch moving.
     
  20. alohazabel

    alohazabel Member
    Messages: 44

    mission accomplished

    Didn't go exactly as planned, but its done...

    The packing nut was really seized in there, and I ended up breaking the top off of the packing nut, so I had to cut the ram off with a sawzall, then I unscrewed the "tube" from the housing, and I was able to get to the threads from the packing nut out by cutting three vertical lines in them with the sawzall and then tapping out the chunks with a chisel with out hurting the threads in the tube

    Went and bought a new ram, packing nut, packing, etc.

    cleaned everything out, put it all back together, filled it with fluid, and it works good.

    new seals, no more leaks.

    thanks again for the help