Any Eaton 13spd experts here?

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Denialator03, Sep 25, 2021.

  1. Denialator03

    Denialator03 Bobtail Member

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    Sep 25, 2021
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    Let me start by saying I've been driving for 20+ years and have experience in everything from a 6spd to an 18spd, but this is the 1st time I've experienced this phenomena in an Eaton 13spd.
    While I was driving a few weeks ago I had a brain fart/daydreaming episode while downshifting... I thought I was in 7L and shifted to 6H... Well as it turns out I was actually in 5L and shifted down into the LOW position with the range switch in High and the splitter in Low.. once I realized what I did I quickly switched over to 4 and noticed that the rpm/speed was the same whether I was in 4 or was in the Lo gear with the range in high and splitter in low. I've confirmed this many times since.
    No mechanics I've talked to could explain it, even a few at some dealerships. They all think there should have been some grinding and I shouldn't have been able to go into Low like that.
    I'm wondering if it's an idiot proof feature for when dummies like myself, or if maybe it's a feature I'm not aware of so you don't have to drop to low range in traffic?
    Any thoughts?
     
    Oxbow Thanks this.
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  3. AModelCat

    AModelCat Road Train Member

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    Called the hidden gear. Even the 18 has it. Some drivers claim to use it all the time, others say its hard on the transmission. I wouldn't use it. I figure if Eaton intended it to be used, they'd have included it in the shift pattern.
     
    Catmando, D.Tibbitt and Denialator03 Thank this.
  4. Denialator03

    Denialator03 Bobtail Member

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    Sep 25, 2021
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    I agree. Since I haven't been able to find any info from Eaton regarding it and it's not shown on the shift pattern sticker I think I'd better avoid it.
    It just peaked my curiosity as I've never heard about before.
    Thanks!
     
  5. MLC Adventures

    MLC Adventures Medium Load Member

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    RPM's are very close. I use it occasionally. Not hard on the tranny if shifted correctly. I have a certification from Eaton that says I know what I'm doing.
     
    lester, Bean Jr., JoeyJunk and 2 others Thank this.
  6. Bean Jr.

    Bean Jr. Road Train Member

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    The first truck I drove when I got a job had a 9 speed. It's pattern was lo through 3 in the low range, then 4-8 on the high side, ie using the lo hole in high range. So using lo in the high range on a 13 speed is ok too, I just don't bother. Use it for one extra split? Not worth it to me.
     
  7. wore out

    wore out Numbered Classic

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    There is nothing to lock it out so to speak. Basically it’s an overlap gear or close to same ratio as the low gear in high side. No big deal really.
     
  8. Dustyroads38

    Dustyroads38 Light Load Member

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    was told about the "hidden" gear. worked out as like having 4h and would use it occasionally to keep from dropping in the lowside momentarily. did lots of off road oilfield trucking and never had an issue with my trans. as far as I'm concerned, use it if you can shift properly. if you can hit it without perfection, i understand you can #### up your tranny bc you have a big gear spinning a little gear. for what its worth the owner of the company i drove for is the one who showed me, so if dude was super concerned about his equipment, i doubt he'd shown it to me.
    on another note, grew up with nothing but 15's, drove a 13 for 7 year, 18 for about a year, and now have my own 15 backed by a two speed. somedays my brain reverts back to the 13/18 pattern and I feel like a #### greenhorn.
     
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  9. lester

    lester Road Train Member

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    I use it everyday multiple time a day. It just works good for me.
     
    D.Tibbitt and Bean Jr. Thank this.
  10. D.Tibbitt

    D.Tibbitt Road Train Member

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    Never knew this gear existed. I want to try it now
     
    Isafarmboy and wore out Thank this.
  11. wore out

    wore out Numbered Classic

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    It’s nothing special......usually makes a little noise. Not saying it’s hurting anything or I hadn’t used it a few times......when it’s the only gear in the box with a little whine makes me nervous lol
     
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