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Old 07-24-2021, 08:11 AM   #1
johnkarenl
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Axle Ratio

My wife and I are retiring in October and are in the process of buying a new TV. We are looking at the 2022 F350 Diesel. My question is what is the best axel ratio to use. The options on the Ford site are:
3.31 non limited slip (included)
3.31 electronic locking
3.55 non limited slip
3.73 electronic locking
3.73 limited slip
4.30 electronic locking
We are currently towing a 1/2 ton version Cougar tt but plan to upgrade to a 5er in the future. The new trailer won’t be longer than 32 ft.
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Old 07-24-2021, 09:06 AM   #2
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What engine/transmission?

It looks like a 350, diesel comes with a 10 speed trans. So I would see if you cant test drive a 3.73 electronic lock. Good luck!
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Old 07-24-2021, 09:06 AM   #3
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Axle ratio, especially with the 10 speed tranny, won’t have as big an impact as it used to in the days of 4-6 speed transmissions. With that said, I’d go for the 3.73 limited slip as a good compromise. If you were going to be towing heavy, I’d take the 4.3. I have the 3.31 limited slip in my signature truck. That year the 3.31 and 3.55 were the only options. I’d prefer the 3.55 or 3.73 for a little better low end starting, but again, the diesel has so much torque that the difference is negligible. The higher geared 3.31 will give marginally better fuel economy when empty, if it’s going to be a daily driver. The 4.3 will give the best low end, but worst fuel economy. The 3.55 and 3.73 will be the best compromises. I’d definitely get the limited slip for better traction. Whichever you decide, the 10 speed tranny will make shifting almost unnoticeable.
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Old 07-24-2021, 10:06 AM   #4
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Absolutely nothing higher than the 3:73 limited clip. Don't let anyone hand you the "much better fuel mileage with the 3:31" baloney. It ain't true.
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Old 07-24-2021, 10:18 AM   #5
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I'd have to agree with the 3:73 as an all round towing & daily driver gearing in either gas or diesel.
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Old 07-24-2021, 10:26 AM   #6
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You're getting 475 horsepower and 1050 ft/lbs of torque with that 6.7 diesel. Axle ratio won't be a concern unless you're going to be hauling max loads over the mountains. My dually has a 3:73 and I'm happy with it hauling my 18K lb Fuzion. The whole rig scales at 26080 lbs.
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Old 07-24-2021, 10:34 AM   #7
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As a "Ford SuperDuty owner" you left out the MOST IMPORTANT AND USEFUL axle ratio. The 3.55 Electronic Locking option....

The 3.55 is the "standard selection" and the 3.55 EL option is probably the most popular and the most useful option.

I have the 3.31 EL option and completely agree with the comment about it NOT offering any fuel mileage improvement. It does "run at lower RPM when on the interstate" but to obtain the "best fuel mileage, I opt to lock out 6th gear when towing" which puts the drivetrain in the same RPM range as the 3.55 in 6th gear. So, NO IMPROVEMENT WITH THE 3.31EL OVER THE 3.55 EL.

With the Ford 6.7L diesel, there is no need for a 3.73 gear ratio. That would put you "screaming down the highway at 70MPH" with no way to upshift. With the 3.55 you'll be running about 1600 RPM at 70MPH which is the "sweet spot" for the Ford diesel.

Now, if you were ordering a gas engine, the 3.73 is the "standard gear ratio" but with the diesel, until you get into "heavy duty, special purpose towing" the two "Ford recommended gear ratios" are the 3.55 and the 3.31 with the 3.55 being the most popular.

DON'T try second guessing the "special purpose options" for "non-special purpose applications"..... Stick with the 3.55 for any fifth wheel towing up to the "DRW requirements".. In other words, under a 13,500 pound GVW fifth wheel, a F350 diesel with 3.55 gearing (LS for 4x2 and EL for 4x4) is probably your best option.
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Old 07-24-2021, 11:05 AM   #8
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I’d like to thank everyone for these responses it is very informative. This forum is always filled with great information. Something I did leave out is the tv will be a 4x2 with an 8ft box.
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Old 07-24-2021, 12:52 PM   #9
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With my 15k 5th wheel I prefer the 3:73 ratio 1800 rpm is just fine.
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Old 07-24-2021, 01:13 PM   #10
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I believe you'll find, if you go to the Ford website and click on "build&price", you'll find that there are ONLY two gear ratio options for the diesel engine. in the SRW trucks. They are the 3.31 and the 3.55. Choices in LS, non LS and Electronic locking features are also restricted in some models depending on engine selection....

Go to the website, click on the axle ratio of your choice, click on the "i" in the circle (information) and read the restrictions.... The 3.73 and the 4.30 are not available in the 1 ton diesel, only in the 1 ton gas trucks..... The first 3.73 optional rear end in a diesel truck is with the F350 DRW series.
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Old 07-24-2021, 01:28 PM   #11
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I believe you'll find, if you go to the Ford website and click on "build&price", you'll find that there are ONLY two gear ratio options for the diesel engine. in the SRW trucks. They are the 3.31 and the 3.55. Choices in LS, non LS and Electronic locking features are also restricted in some models depending on engine selection....

Go to the website, click on the axle ratio of your choice, click on the "i" in the circle (information) and read the restrictions.... The 3.73 and the 4.30 are not available in the 1 ton diesel, only in the 1 ton gas trucks..... The first 3.73 optional rear end in a diesel truck is with the F350 DRW series.
John, you know that I have no use for any pickup without dual rear wheels, heck my granddaughter is wanting a dually for school at Texas Tech 😉
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Old 07-24-2021, 01:38 PM   #12
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John, you know that I have no use for any pickup without dual rear wheels, heck my granddaughter is wanting a dually for school at Texas Tech 😉


Javi tell her to be sure and measure those spaces!!! My daughter graduated from TT in 95 and we were in and out of there a lot. I was in Lubbock the other day killing time and decided to drive through Tech after all these years. Oh boy, that place has grown like a weed and people/folks are packed (to me). At least the IHOP and little pizza place we used to take my daughter were still there but not much else.
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Old 07-24-2021, 01:43 PM   #13
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John, you know that I have no use for any pickup without dual rear wheels, heck my granddaughter is wanting a dually for school at Texas Tech 😉
If your "GD" is like my "GD" she'll get what she wants and grand daddy will help pay the part she couldn't manage..... Ain't they special creatures (in spite of having my daughter for a parent) ROFL
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Old 07-24-2021, 01:46 PM   #14
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Javi tell her to be sure and measure those spaces!!! My daughter graduated from TT in 95 and we were in and out of there a lot. I was in Lubbock the other day killing time and decided to drive through Tech after all these years. Oh boy, that place has grown like a weed and people/folks are packed (to me). At least the IHOP and little pizza place we used to take my daughter were still there but not much else.
This is her second year and she is moving out of the Honors dorm into a 5 bedroom townhouse with her sorority sisters/roommates from last year. One of the girls is on the TT shooting team 👍
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Old 07-24-2021, 01:51 PM   #15
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If your "GD" is like my "GD" she'll get what she wants and grand daddy will help pay the part she couldn't manage..... Ain't they special creatures (in spite of having my daughter for a parent) ROFL
Pretty proud of her, she made the Dean's list in Honors with a 4.0 GPA
Finance/accounting and pre-law
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Old 07-24-2021, 02:15 PM   #16
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This is her second year and she is moving out of the Honors dorm into a 5 bedroom townhouse with her sorority sisters/roommates from last year. One of the girls is on the TT shooting team 👍

Much better! That's what my daughter did then we just moved her into a house of her own junior and senior years. Lot more room for your DGD's DRW. And I agree; on the shooting team.
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Old 07-24-2021, 02:16 PM   #17
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Pretty proud of her, she made the Dean's list in Honors with a 4.0 GPA
Finance/accounting and pre-law

Saw a maroon 350 DRW at the local dealership a while back.....might still be there......
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Old 07-24-2021, 10:17 PM   #18
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I'll just tell you what I had. First truck was F-350 SRW with the diesel and 3.55, and it drove beautifully and seemed to have plenty of power for just about anything. Pulled many trips moving all our worldly possessions in a 24' cargo trailer with no issues at all. Then I bought the world's biggest 5er, not knowing I had too little truck. Pulling it up our steep hill made it feel like the truck was going to drop the tranny right there, so when I eventually traded in for the dually, I got it with the 4.10. It is much slower in general, but still lopes up to 80mph smoothly when unladen, and pulls hills with any trailer like a champ. I'm very comfortable driving 70mph with the camper, and it definitely lets me know when I'm approaching 75. I'm glad I got the higher ratio, but I wish the 3.73 had been an option, as I think that would have been the better compromise. One thing I've learned is to definitely use the gear limiter when I'm going slowly up hills, or it tries to shift too early and feels terrible.
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Old 07-29-2021, 07:26 AM   #19
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Quote:
Originally Posted by johnkarenl View Post
My wife and I are retiring in October and are in the process of buying a new TV. We are looking at the 2022 F350 Diesel. My question is what is the best axel ratio to use. The options on the Ford site are:
3.31 non limited slip (included)
3.31 electronic locking
3.55 non limited slip
3.73 electronic locking
3.73 limited slip
4.30 electronic locking
We are currently towing a 1/2 ton version Cougar tt but plan to upgrade to a 5er in the future. The new trailer won’t be longer than 32 ft.
I have a 2021 F350DRW with the 4:10 limited Slip. Pull a 40 ft 6 slide Alpine. You barely even notice RV is hooked up. RPM's aren't that bad . Think I've seen close to 2000 RPM around 70 MPH but it's still very quiet inside the cab. Gone up some grades and tranny stays in 10th gear and doesn't slow down.
I've owned various brands of trucks to include GMc,Chevy,Dodge Ram and have stuck with FORD. Have owned several Super Duties with various gear ratios, 3:31,3:55,3:73 and 4:10's . Can't really say I've noticed any big difference although I prefer my 10 speed over the 6 speed tranny. Keep in mind these new trannys run hot and the cooling fan comes on more often in hot weather even if not towing . Sounds like a big rig at times when taking off from a stop.
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Old 07-29-2021, 07:42 AM   #20
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My experience and what I drive is a 3.73 electronic lock I tow a 2016 Alfa Gold SH scaled at 19,785 lb loaded ( 1/2 tand of water) and never had a problem.
F350 DRW 6.7 DI 3.73 Diff. I have made 4 cross country trips I 90,I 40, I 10 Rt 66. and Rt50. and I some times have to look to see if the trailer is behind me and I still average 14.5 MPG. by the way I worked Ford Service departments for 35 years, as a tech and in management my last 20 years as the Service Director.
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