7.3 idi c6 mpg

[jayro88]

Yeah starting to wonder about bearings or something. Deff seems like i have some rolling resistance the more i hash it out on the forum. I did the math and should be around 2350 rpm at 60 not at the nearly 3000 I'm at. So going to look into that this weekend. Thanks for all the help.

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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[IDIBRONCO]

I did the math and should be around 2350 rpm at 60 not at the nearly 3000 I'm at.

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?

 

[crr31c]

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.

 

[IDIBRONCO]

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.

 

[crr31c]

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

 

[jayro88]

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

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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[Hydro-idi]

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

 

[Cubey]

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

 

[IDIBRONCO]

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

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