High Rpm....low speeds

Discussion in 'Ask An Owner Operator' started by trucky909, Sep 20, 2020.

  1. singlescrewshaker

    singlescrewshaker Road Train Member

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    Transmission Ratio RPM Calculator | Spicer Parts

    There's the link..
    This is my rpm, road speed for all gears at 1800rpm. Speed in box, ratio for each lever position above boxes..
    RTX 12609B. 4.10 rear, 11r22.5 tires
    Notice even at redline, about a 500rpm drop ~1800-1300rpm
    Low-1 gains 2.9mph
    1-2 gains 3mph
    2-3 gains ~4mph
    3-4 gains 5mph
    4-5 gains 8mph
    5-6 gains 11mph
    6-7 gains 15mph
    7-8 gains 20mph
    20200926_125148.jpg

    Did you ever verify the actual trans model you have.? I think you said FR 15210 or something.? Check the model # on the case to make sure it matches the model # in the glove box..

    On my picture, in black ink shows what the ratio is for the Low hole, but in high range. Effectively, it's like a 3.5 gear between 3 & 4 low range. So if someone stole your 10speed, put a 9 in there like mine, when you "think" you're shifting from 5 low to 6 high, you might really be shifting 4 low to Low high, or like a 3.5 gear effectively gaining no speed till you shift to 7th. Really the 5th position if it's a 9 speed.. Just a thought.. Here's the pattern to help visualize what I'm trying to convey..

    1818-20398-3.jpg

    10-speed-shift-pattern-Eaton-Fuller.png
     
    Rideandrepair Thanks this.
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  3. trucky909

    trucky909 Light Load Member

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    Ok thanks alot....yes the mechanic said everything matches on the transmission side of things. And this was my first time going to this guy.

    So its ok for me to take the rpms to 1800?

    I'll review everything you've sent...thanks again...helps me look at things differently now.
     
  4. AModelCat

    AModelCat Road Train Member

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    1800 ain't gonna hurt anything. Most big bore diesels are governed to around 2000 to 2100 RPM. 1650-1750 seems to be the sweet spot, at least on the older engines anyways.
     
  5. singlescrewshaker

    singlescrewshaker Road Train Member

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    Here, I did it for you because I was bored. Everything seems to match up with what you are saying. Just a direct drive trans in action. Probably not the best spec for running local if that what you are doing with it..

    20200926_140412.jpg


    This screen shot matches up pretty well with the 7th gear picture you posted IMO..
    Screenshot_20200926-140348_Samsung Internet.jpg
     
  6. singlescrewshaker

    singlescrewshaker Road Train Member

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    Math looks pretty spot on..
    Again these are all for 1500rpm
    20200926_140412.jpg

    Your 6th @ 1475rpm looks like 20mph on the
    speedo
    Screenshot_20200926-155031_Samsung Internet.jpg
    20200925_162242.jpg

    Your 7th @ 1400rpm looks like 25mph on the speedo
    Screenshot_20200926-155432_Samsung Internet.jpg

    20200925_144854.jpg

    Either your tachometer or speedometer was off at one point, or your memory has slipped on this one..

    This is all I can figure..
     
  7. trucky909

    trucky909 Light Load Member

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  8. Eldiablo

    Eldiablo Medium Load Member

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    There’s nothing wrong with it.
     
  9. Ridgeline

    Ridgeline Road Train Member

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    A few things and I won’t say anything else.


    First is this isn’t a clutch issue, never was. The clutch slipping would still not cause this issue so replacing the clutch was a waste of money.

    second is the mechanic is a ... well I can’t post what I think but to me he is a pos parts changer, and you - op - should consider suing him. One thing that the mechanic should have done is check the actual speed, if the shop has a dyno, stick it on the dyno and see the actual wheel speed or at least to take the truck for a ride with a second mechanic following him to determine the actual speed, nothing less than this.

    third the op has some holes in his story, and what he needs to do is go to a mechanic or a shop that is not just certified to fix the engine but also has the factory diag system to stick the truck on the computer to see what was screwed up because I am thinking that the stupidity of deleting the emissions system screwed a lot more up than what appears to be screwed up, one reason why I dump any truck I get that has been deleted as fast as possible.
     
  10. AModelCat

    AModelCat Road Train Member

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    How was it not described as a clutch issue? OP stated the RPM was higher in each gear, climbed faster than the speed and I believe it was mentioned it was worse when loaded. Classic clutch slippage symptoms. Not our fault OP couldn't effectively describe the symptoms.
     
    Last edited: Sep 27, 2020
  11. Brettj3876

    Brettj3876 Road Train Member

    The dd routinely go 22-23 under full jake with the autos 1800 is fine. You said it's deleted and probably putting down some more horse? Change up your driving habits if you want any longevity from it. Lugging a diesel that's been turned up some is putting even more stress on the bottom end. Don't be afraid to hold it 1700-1800 on a pull. And get a pyro if you don't already have one.

    Take that down speeding fleet Bean counter bs and forget you ever heard of it
     
    trucky909 and singlescrewshaker Thank this.
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