Changing Gear Ratio in Rear End to 3.55 on 7.3L Godzilla
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Trailering
Joined: Apr 2022
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Changing Gear Ratio in Rear End to 3.55 on 7.3L Godzilla
Hello: Any experience or thoughts on changing rear end to a 3.55 ratio from the stock option 3.77 for the 7.3L Godzilla? The motor has excellent low end torque, love to get a couple more MPG. With the 10spd transmission, this shouldn't be an issue affecting my drivability.
Fleet Mechanic
Joined: May 2018
Posts: 1,765
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My thought is you'd never recoup the cost of a gear swap with MPG savings. With the 10 speed, I wouldn't expect any noticable difference in MPG going from 3.73 to 3.55. That's not much of a jump, especially when you have the 10 speed transmission to start with. Best bet for better MPG's is modifying your driving habits.
Tuned
Joined: Jul 2005
Posts: 353
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My thought is you'd never recoup the cost of a gear swap with MPG savings. With the 10 speed, I wouldn't expect any noticable difference in MPG going from 3.73 to 3.55. That's not much of a jump, especially when you have the 10 speed transmission to start with. Best bet for better MPG's is modifying your driving habits.
Pretty much what he just said. If it’s 4x4 you have to do both diffs and I can’t see the cost would ever make that small of a gear change worth it. Just be easy on the throttle and don’t drive aggressively or fast
5th Wheeling
Joined: Mar 2020
Posts: 35
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you would be saving like 75 RPM at 75MPH.....
https://spicerparts.com/calculators/...rpm-calculator
I regarded my old 2016 F-150 3.5 EB FX4 from 3.31's to 4.10s. It was a few sheckles shy of 3 grand installed.
https://spicerparts.com/calculators/...rpm-calculator
I regarded my old 2016 F-150 3.5 EB FX4 from 3.31's to 4.10s. It was a few sheckles shy of 3 grand installed.
Mountain Pass
Joined: Dec 2021
Posts: 242
Likes: 102
Waste of Time and money. If you got extra of both go for it.
I did gears on my 6.4 Hemi. Went from 4:10 to 4:88. Was there a difference yes. Was there a $3000 difference nope.
what you will pay to do gears buys a whole bunch of fuel. You might gain .5mpg
I did gears on my 6.4 Hemi. Went from 4:10 to 4:88. Was there a difference yes. Was there a $3000 difference nope.
what you will pay to do gears buys a whole bunch of fuel. You might gain .5mpg
5th Wheeling
Joined: Mar 2020
Posts: 35
Likes: 14
You could gain more then that by driving habits.....and keeping the highway speeds reasonable, fuel consumption really falls off the face of the earth above what, 72-75?
Tuned
Joined: Sep 2020
Posts: 267
Likes: 79
From: San Antonio
I've found that driving 65-70 on the highway (even in 75MPH speed limits) gets me the best mileage on my 2017 F-250. If I jump up to 75-85, forget it. Yeah, I can keep up with anyone on the road, but when my mileage goes from 17-20mpg down to 14-15mpg, it's not worth the extra MPH to get there faster. I just leave a little earlier or plan on arriving a little later.
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Laughing Gas
Joined: Aug 2021
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I made a 200 mile highway runs with a small amount of city driving. My actual MPG was 18.3 mpg while the dash monitor said 15.2mpg. I was surprised that it was that far off. 7.3L with 4.30 gears.
Bob
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5th Wheeling
Joined: Mar 2020
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Agreed, and make sure that you are hand calculating the mileage.
I made a 200 mile highway runs with a small amount of city driving. My actual MPG was 18.3 mpg while the dash monitor said 15.2mpg. I was surprised that it was that far off. 7.3L with 4.30 gears.
Bob
I made a 200 mile highway runs with a small amount of city driving. My actual MPG was 18.3 mpg while the dash monitor said 15.2mpg. I was surprised that it was that far off. 7.3L with 4.30 gears.
Bob
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Trailering
Joined: Apr 2022
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I would like to thank all those that replied. Special thanks to Jmo371, who provided the link with the Spicer Parts RPM calculator. Easy to use and provides number creditability that went with the forum consensus.
