4MG 3406B jake brake

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by mile marker 27, Jan 2, 2026 at 11:23 AM.

  1. mile marker 27

    mile marker 27 Road Train Member

    1,351
    1,707
    Dec 4, 2019
    0
    Jakes will pull engine all the way down until it stalls. I don’t have a “low” setting. The switch is either “off” or “high”.
     
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  3. Oxbow

    Oxbow Road Train Member

    13,368
    138,448
    Nov 24, 2015
    Idaho
    0
    If you touch the throttle or the clutch it kicks the jakes out, right?
     
  4. mile marker 27

    mile marker 27 Road Train Member

    1,351
    1,707
    Dec 4, 2019
    0
    Yes.
     
  5. wore out

    wore out Numbered Classic

    16,748
    204,874
    Jun 5, 2013
    CHASIN THE DEVIL'S HERD
    0
    They are set up forward cylinders or rear. I’ll be honest just half of them are the most useless thing on the truck. With both working together they are the 2nd most useless thing on the truck. I’d run it
     
    ElmerFudpucker and Oxbow Thank this.
  6. mile marker 27

    mile marker 27 Road Train Member

    1,351
    1,707
    Dec 4, 2019
    0
    Ok, woreout, I’m in your lane here. Should the jakes kill the engine, even if the accelerator or clutch, isn’t depressed? My old big cams don’t.
     
    MACK E-6 and Oxbow Thank this.
  7. wore out

    wore out Numbered Classic

    16,748
    204,874
    Jun 5, 2013
    CHASIN THE DEVIL'S HERD
    0
  8. mile marker 27

    mile marker 27 Road Train Member

    1,351
    1,707
    Dec 4, 2019
    0
    Well, I guess I’ll leave the mf’er alone. Now, I’m wondering why the BC’s I have don’t do the same? My electronic engines(12.7 and N14) don’t stall either but that’s electric fuel delivery.
     
    MACK E-6 and Oxbow Thank this.
  9. wore out

    wore out Numbered Classic

    16,748
    204,874
    Jun 5, 2013
    CHASIN THE DEVIL'S HERD
    0
    The electronic motors it’s in the ECM to shut them off under 800.

    It’s been a long time and I can’t remember what the name of this control box was it was an add on thing like king cruise. Only it shut the Jake’s off at idle.


    I flip my switch it’s just sorta 2nd nature to me
     
    MACK E-6, mile marker 27 and Oxbow Thank this.
  10. SmallPackage

    SmallPackage Road Train Member

    5,700
    18,210
    Dec 20, 2019
    Marion Texas
    0
    Jakes will stall the engine out. Even a Cummins if it is wired straight to heads without throttle or clutch switch like many early one were. It will take it from 2200 rpm to shut down in a matter of seconds. My 25A’s on my 350 are just a on/off toggle and a 3 position toggle for 1 head or 2 heads, or all 3 heads.
     
    Oxbow Thanks this.
  11. SmallPackage

    SmallPackage Road Train Member

    5,700
    18,210
    Dec 20, 2019
    Marion Texas
    0
    Many Old timers that ran the old two stroke Detroit's have said that they were the only engine you could leave the jakes on at idle. They would not stall the engine. Lol
     
    MACK E-6 and Oxbow Thank this.
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.