Eaton Fuller 10SP grind when downshfting

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by MIg25, May 31, 2020.

  1. MIg25

    MIg25 Bobtail Member

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    Hello,
    I have a freightliner FL112 with a 10SP Eaton Fuller, when I am downshifting from 6th to 5th, I flip the switch it grinds very badly. Basically I have to stop the truck, flip the switch for it to drop gears.
    Any advise or input?
    Thank you.
     
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  3. AModelCat

    AModelCat Road Train Member

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    Sounds like a synchronizer issue.

    I'd start by checking the air pressure to the range cylinder. There's a regulator on the transmission that drops it down lower than air system pressure. Can't remember the exact PSI spec.

    There should be an air filter in there too that can get gummed up and make it lazy. There's also an exhaust port that can get plugged up and prevent air from dumping out of the range piston as well.
     
    Last edited: May 31, 2020
  4. MIg25

    MIg25 Bobtail Member

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    Is the air pressure range cylinder and the filter all mounted on the transmission itself? Where at?
    Indeed, when I am idling I flit the switch up goes fine, down it is a little lazy for sure.
     
  5. AModelCat

    AModelCat Road Train Member

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    Should be somewhere on the transmission. Not 100% sure exactly as to where they'd be on a 10 speed.
     
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  6. MIg25

    MIg25 Bobtail Member

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    I think this is the filter you speak of. See picture below with red arrow.

    eaton filter.JPG
     
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  7. baha

    baha Road Train Member

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    it should be hanging on back box, it unscrews and you can get water plus what/ever is caught in filter when you blow it out, its just a filter in the filter canister that un screws?
     
  8. pushbroom

    pushbroom Road Train Member

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    Low air pressure usually makes slow shifts. If it actually grinds you need a syncro
     
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