7.3 idi c6 mpg

Discussion in '6.9L IH & 7.3L IDI Diesels' started by crr31c, Nov 7, 2018 at 11:04 PM.

  1. jayro88

    jayro88 Full Access Member

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    I thought the RPMs were kinda high for your setup and speed. That’s why I was asking about the 3.55 gears. But even with 4.10s I would think you should be getting over 10mpg at 65mph. Heck, I get about 10mpg while towing my 30’ travel trailer and EGTs hovering in the 1000* range.


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  2. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    This is what makes me wonder if your transmission is slipping in drive. Those RPMs are just way too high. Do you know the condition/mileage of your transmission?
     
  3. crr31c

    crr31c Registered User

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    Rebuilt 2 years ago. By previous owner. Flushed converter and tranny and be filter and modulator and seals a couple months ago when i built engine. But this big girl won't coast at all. Thought it was just the gearing. Been a long time since i had a 3 speed. But when i let of the gas. I almost don't even need brakes to stop.
     
  4. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Hopefully something is dragging and will be simple to fix. If there is something dragging, the transmission could be slipping which could be causing the high RPMs.
     
  5. crr31c

    crr31c Registered User

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    Will look at this weekend and let y'all know what i find
     
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  6. jayro88

    jayro88 Full Access Member

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    If you have an IR temp gun you can always drive for a while and then take temp measurements of the hubs. If 1 or 2 are noticeably hotter than the others then you found the culprit.


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  7. Hydro-idi

    Hydro-idi Full Access Member

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    If I recall, mine cranked around 2600 rpm @ 60mph. 6.9 with C6 & 3:55’s. Sounds like you might have 4:10 gears...
     
  8. Cubey

    Cubey Full Access Member

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    Don't worn injectors kill mpg as much as the IP? Maybe its a combination of many things.
     
  9. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Yes, but he did say that he changed out the 4.10s for 3.55s. So he knows that they are 3.55 gears.
     

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