Gears Vs MPG
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Senior User
Joined: Nov 2009
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Gears Vs MPG
Hey guys. Got a question. I currently have 3.73's in my 03 with auto. I'm going to change to 4.30's to help with towing. My truck is one of those V10's that gets 14-16 mpg(8 towing). I'm wondering how much this will drop when I change gears.
Oh yeah truck is mostly stock, except 5star tunes and custom exhaust, which includes headers, dual pipes past cab into high flow converter into 4" race bullet and single 3" tailpipe.
Oh yeah truck is mostly stock, except 5star tunes and custom exhaust, which includes headers, dual pipes past cab into high flow converter into 4" race bullet and single 3" tailpipe.
Former Vendor
Joined: Sep 2000
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From: South Carolina
Hi VAXB
I think 4.30 gears are a great investment. Hwy you might see a drop of 1 or 2 mpgs max. Towing i think you would see about the same 8 mpg ish. Once you do swap out gears let me know so i can revise your tunes for you.
Mike
I think 4.30 gears are a great investment. Hwy you might see a drop of 1 or 2 mpgs max. Towing i think you would see about the same 8 mpg ish. Once you do swap out gears let me know so i can revise your tunes for you.
Mike
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Senior User
Joined: Nov 2009
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Thanks Mike. Since you answered, i have a question for ya. I can Hi-jack my own thread!
I love the shift strategies of the tow tune, is there any long term effect of running the tow tune all the time.
I love the shift strategies of the tow tune, is there any long term effect of running the tow tune all the time.
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Joined: Oct 2004
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When I did my swap, fuel economy remained the same, with a few caveats. With the 3.73 gears, I got my best highway mileage, 13 mpg, at 80 mph. If I dropped back to 70, I'd get 11 - 12. With the 4.30 gears, I get 13 mpg still, but at 70 mph. Run it up to 80, and she'll drop down to 10 - 11 mpg.
This is all hand-calculated 3-hour trips running the same routes. By no means scientific, but enough to know what speed she likes for economy.
I have not towed yet with the 4.30 gears, but with the 3.73's it would get a solid 9 mpg, whether the trailer was empty at 6500 lbs to a medium load at 11,500+ lbs. It would, however, take me a good 1.5 to 2 miles to get up to 70 when loaded. The 4.30's should improve things. I should mention that the trailer is my old man's 20k lb. capacity gooseneck dump trailer with tandem duals -- and it pulls hard for its weight.
Also, city mileage seems to be up about 1 mpg, but I need more time to get a good, solid average given the many variables associated with city traffic.
This is all hand-calculated 3-hour trips running the same routes. By no means scientific, but enough to know what speed she likes for economy.
I have not towed yet with the 4.30 gears, but with the 3.73's it would get a solid 9 mpg, whether the trailer was empty at 6500 lbs to a medium load at 11,500+ lbs. It would, however, take me a good 1.5 to 2 miles to get up to 70 when loaded. The 4.30's should improve things. I should mention that the trailer is my old man's 20k lb. capacity gooseneck dump trailer with tandem duals -- and it pulls hard for its weight.
Also, city mileage seems to be up about 1 mpg, but I need more time to get a good, solid average given the many variables associated with city traffic.
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Senior User
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Sounds good. Mileage is not the most important factor, its not a daily driver. I just didn't want to end up getting 9 all the time.
The truck pulls my 8klb camper OK, just seems happier doing it closer to 2K rpm's. Now when it hits OD it's about 1800 at 65 and it seems to struggle a bit. I was thinking the 4.30's would get me closer to the meat of the powerband while cruising 65-70.
Thanks for the replies.
The truck pulls my 8klb camper OK, just seems happier doing it closer to 2K rpm's. Now when it hits OD it's about 1800 at 65 and it seems to struggle a bit. I was thinking the 4.30's would get me closer to the meat of the powerband while cruising 65-70.
Thanks for the replies.
Former Vendor
Joined: Sep 2000
Posts: 2,627
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From: South Carolina
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Postmaster
Joined: Oct 2008
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From: Richmond BC
i wouldnt be surprized if you gain MPG, since your truck will hold OD better, resulting in more times the engine wont be lugging or forced to drop into 3rd gear...
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When I did my swap, fuel economy remained the same, with a few caveats. With the 3.73 gears, I got my best highway mileage, 13 mpg, at 80 mph. If I dropped back to 70, I'd get 11 - 12. With the 4.30 gears, I get 13 mpg still, but at 70 mph. Run it up to 80, and she'll drop down to 10 - 11 mpg.
This is all hand-calculated 3-hour trips running the same routes. By no means scientific, but enough to know what speed she likes for economy.
This is all hand-calculated 3-hour trips running the same routes. By no means scientific, but enough to know what speed she likes for economy.
I see the exact same thing. With 3.73's, if I hold 80, I get better mileage than if I hold 70. There's some blip on the torque curve in the Ford literature for the PI head V10 that occurs right around those two speeds. I think the blip corresponds to 70MPH with 3.73's. Interesting stuff...
To VAXB: You may or may not notice a difference. The modulars don't respond in the classical sense to lower gearing using more gas. Your mileage may vary !
