Final drive ratio
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More Turbo
Joined: Mar 2024
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From: SE Vermont, South Jersey
Final drive ratio
Looking at a crew cab F250/7.3 gas crew cab short bed, the default is 3.73. Besides being my commuter vehicle (super long 11.8 miles one way) the primary purpose of upgrading from a 1/2 ton will be to tow a 9-10k travel trailer. I have always gone with the lowest (highest number) gears, but it seems like with a 10 speed tranny that even the 3.55 gears* would be "OK".
We will be towing in every possible reasonable road conditions throughout the lower 48, probably some Canada and Alaska.
*I will be going with the "locking" option. BTW - what is that/how does it work? Is it automatic and a full-on lock? Manually lock? LSD? Curious because the default is a "non-limited slip" from which I infer that a limited-slip is available but the options are for an "Electronic locking"
We will be towing in every possible reasonable road conditions throughout the lower 48, probably some Canada and Alaska.
*I will be going with the "locking" option. BTW - what is that/how does it work? Is it automatic and a full-on lock? Manually lock? LSD? Curious because the default is a "non-limited slip" from which I infer that a limited-slip is available but the options are for an "Electronic locking"
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
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From: Stephensville WI
The locking differential is an electronic locker. You lock the diff by pulling out the 4x4 selector ****. The truck automatically disengaged the locker if you exceed 20 MPH or so. With the locker disengaged the differential is an open set.
Cargo Master
Joined: Apr 2021
Posts: 2,571
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From: Bighorn Basin, NW Wyoming
Gears are a very sensitive topic on this forum, as you will find out. Some people on here love the 7.3 with 3.55’s, I didn’t.
I didn’t so much that I traded it in for the same exact truck with 4.30’s.
I didn’t so much that I traded it in for the same exact truck with 4.30’s.
Laughing Gas
Joined: Apr 2023
Posts: 904
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From: SE PA
For what you are towing 3.73 should be fine, 3.55 probably would be ok and will give slightly better mpg. There is no limited slip diff available. The locker is enabled by a button on the 23+ and it will disengage automatically at the design speed of 25MPH and re-engage when you slow down below 25MPH.
BTW; There are some on here that 4.30's are the only way to go even if you don't have the load that requires it.
BTW; There are some on here that 4.30's are the only way to go even if you don't have the load that requires it.
Logistics Pro
Joined: May 2022
Posts: 4,281
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From: Everywhere and nowhere
Having towed 70% more weight with 3.73s than you are looking to tow, it will be just fine. Especially if your trailer profile is smaller than mine was. There won't be a grade you can't climb at the speed limit with 3.73s towing 10k lbs.
Tuned
Joined: Nov 2023
Posts: 431
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For what you are towing 3.73 should be fine, 3.55 probably would be ok and will give slightly better mpg. There is no limited slip diff available. The locker is enabled by a button on the 23+ and it will disengage automatically at the design speed of 25MPH and re-engage when you slow down below 25MPH.
BTW; There are some on here that 4.30's are the only way to go even if you don't have the load that requires it.
BTW; There are some on here that 4.30's are the only way to go even if you don't have the load that requires it.
Cargo Master
Joined: Apr 2021
Posts: 2,571
Likes: 1,654
From: Bighorn Basin, NW Wyoming
For what you are towing 3.73 should be fine, 3.55 probably would be ok and will give slightly better mpg. There is no limited slip diff available. The locker is enabled by a button on the 23+ and it will disengage automatically at the design speed of 25MPH and re-engage when you slow down below 25MPH.
BTW; There are some on here that 4.30's are the only way to go even if you don't have the load that requires it.
BTW; There are some on here that 4.30's are the only way to go even if you don't have the load that requires it.
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More Turbo
Joined: Mar 2024
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From: SE Vermont, South Jersey
This will be an Airstream. Which supposedly has near ridiculous aerodynamics if you listen to them.
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3.73 + 10 speed + DD with an Airstream occasional tow = 
If we were talking 6 speed the 4.30 for sure, but the low ranges on the 10 speed more than make it up. The only real difference is you might be in 9th at 70 instead of 10th. Big deal.
If we were talking 6 speed the 4.30 for sure, but the low ranges on the 10 speed more than make it up. The only real difference is you might be in 9th at 70 instead of 10th. Big deal.
Cargo Master
Joined: Jul 2011
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From: Walpole, MA
Logistics Pro
Joined: May 2021
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Urgh, I really want a VW XL1 chassis but with a Ford Fiesta's DLD motor and manual gearbox, for solo run about and for commuting I don't need a truck and a small long legged diesel like that would be the bees knees.
Logistics Pro
Joined: May 2021
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But I also don't run 35 inch tires so that helps. With 4.30 if one runs 35s it's only 5% lower gearing than a 3.73 running 32 inch tires, so if one is not going to upsize in tires both the current gearings Ford offers will do fine.
Trailering
Joined: Aug 2016
Posts: 17
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I just tried to do a build and select the 3.55 with the 7.3L gas engine and it brings up the dialog that says it will add the diesel and remove the gas engine. So, it looks like even though it shows as an option, it is only for the diesels.