which axle ratio
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3rd Gear
Joined: Apr 2019
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which axle ratio
. I am currently pulling a new 16k 5th wheel with a 05 F250 6.8l v10 and 4.30 gears. Looking to upgrade to a f350 diesel. Is the 3.55 or 3.73 enough gear for the 6.7. I have found several with a 4.10 gear but how is the fuel mileage with 4.10.
Fleet Mechanic
Joined: Oct 2006
Posts: 1,351
Likes: 242
From: North Florida
With this 10 speed transmission, I’m running 3:31 and pulling 16,000 pounds (fifth wheel) around like it’s a utility trailer. My 2016 had 3:55’s with the 6 speed, and this new truck pulls better than that one.
Sick 'n Tired
Joined: May 2006
Posts: 2,969
Likes: 47
From: League City, TX
I've had 3.55 thru 4.30s across several 6.7Ls and it's anywhere between 9mpg and 12mpg towing the 5th wheels I've had. My current setup is a 450 with 4.30 ratio and unloaded I get between 16-17.5mpg doing 75 on the freeway (slightest wind makes a difference). Towing my current RV which is about 16K, it's generally around 9mpg. But I also drive the speed limit on the interstate. If I kept it to 60-65mpg I'd probably be 10mpg or better.
Laughing Gas
Joined: Jul 2017
Posts: 1,203
Likes: 512
It's not bad, but I wish my F-450 with 4.30 gears and 6.7 was geared a bit taller towing a 15K 40' enclosed race trailer. It takes a pretty good grade to make it downshift from 6th to 5th at 65-75mph on the highway, but It's nice on the real steep mountain grades. I make 9mpg towing the trailer and 14-15 empty on the highway and 12-13 in town. A 3.73 ratio with the 10 speed in this truck seems like it would be a good combo.
Lead Driver
Joined: Nov 2005
Posts: 8,466
Likes: 4,962
And, if you're finding some with 4.10's, then you must be looking at dually's, right?
Any 16K GVWR 5th wheel is well within the range of a SRW diesel truck.
I have a 22 F250 diesel and it is rated high enough to tow a 16K trailer, and that is with a 3.31 gear.
Hotshot
Joined: Mar 2017
Posts: 10,163
Likes: 1,373
From: Chaz
I have this same truck but in a 2wd with 3.55 gears. Same stock size tires.
I am getting 17 mpg lifetime but lots of city driving and I some times am putting it to the floor. I have probably towed 2,000 miles out of the 9,000 I put on it and one leg of that was around 600 miles with a strong headwind and getting 7-8mpg to maintain highway speed.
The 2020+ is a pretty decent upgrade over the 17-19.
Long story short, simply either gear will work with that load if you keep it on tires rated for the stock wheel width. The 4.10 may net out better mpg if its a tow rig.
If you get a single rear wheel f350 make sure it comes with the 18 or 20 inch AT tire so you get the higher rear GAWR. I think it should be around 7200.
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Hotshot
Joined: Jun 2003
Posts: 12,343
Likes: 4,369
From: SW VA
4.10's behind the 6.7 in a dually would be an awesome pulling machine.
Lower gears (higher number) are always better for towing.
Lower gears (higher number) are always better for towing.
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Lead Driver
Joined: Jan 2002
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From: Itinerant
My '16' dually has 3.73 gears and towing the 5th wheel of 16k# in the west at higher elevation/ grades no issues at all and at times actually have to back off a little or it will just keep accelerating up the grade. Mileage towing 9.5-10.5 depending on how much of a hurry I'm in.
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3rd Gear
Joined: Apr 2019
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Yes my f250 is rated to tow a 15800 5th wheel but I am overloaded on the max gvw for the rear axle. There for I will go dually to solve any future changes in trailers. Thanks for the replies. It looks like I will go with the 373 or even the 355.If i am going to upgrade to the diesel I want the best mpg I can get. I have towed with my v10 for many years and i am getting ready to travel more.
Last edited by training; Jul 9, 2022 at 10:25 AM.
Hotshot
Joined: Mar 2017
Posts: 10,163
Likes: 1,373
From: Chaz
If it is just towing get the 4.10 or 450 with 4.30.
But I can vouch with stock tires and 3.55 the dually is pretty stout and gets decent mpg empty. If you dont need 4wd the 2wd gets even better mpg. I like my supercab 2wd 2020, its too much truck for me and I am getting back into a CCSB in the next couple months.
You should watch the order banks as you will get a 23.
But I can vouch with stock tires and 3.55 the dually is pretty stout and gets decent mpg empty. If you dont need 4wd the 2wd gets even better mpg. I like my supercab 2wd 2020, its too much truck for me and I am getting back into a CCSB in the next couple months.
You should watch the order banks as you will get a 23.
Tuned
Joined: Dec 2021
Posts: 429
Likes: 126
6.7L 3.55:1 11k RV
Howdy,
I have a '22 F-350 SCLB Lariat, 6.7L, 3.55:1, w/275-65R20E and tow an 11k RV with no troubles. Fuel economy at 50-55mph is 12mpg with a gentle foot. Speed up to 65-70mph and get 10mpg. Unloaded empty truck with Tremor front panel, Steelcraft Grill Guard and front hitch at 55mph is 20+mpg and 70mph is 18.4mpg. Note: The tire size has not been corrected from OEM 18" which is +2mph at 53mph and +3mph at 67mph per GPS.
The 2022 is quieter, shifts better and uses less DEF than my 2020 did, but the throttle response is slightly slower. The '20 XL STX GVWR was 11,500lbs vs '22 Lariat GVWR 11,400lbs.
BDWSD22
I have a '22 F-350 SCLB Lariat, 6.7L, 3.55:1, w/275-65R20E and tow an 11k RV with no troubles. Fuel economy at 50-55mph is 12mpg with a gentle foot. Speed up to 65-70mph and get 10mpg. Unloaded empty truck with Tremor front panel, Steelcraft Grill Guard and front hitch at 55mph is 20+mpg and 70mph is 18.4mpg. Note: The tire size has not been corrected from OEM 18" which is +2mph at 53mph and +3mph at 67mph per GPS.
The 2022 is quieter, shifts better and uses less DEF than my 2020 did, but the throttle response is slightly slower. The '20 XL STX GVWR was 11,500lbs vs '22 Lariat GVWR 11,400lbs.
BDWSD22
Cargo Master
Joined: Oct 2005
Posts: 2,866
Likes: 515
From: WNY
With the 10 speed, gear ratio is not as critical as before.
I tow roughly 10K in western NY, and honestly it is a joke to think I need a lower gear for even twice the weight.. When you read others say that you didn’t know that you were towing? It’s true..
That said, given what you may tow, the height of the trailer/wind resistance, the area of the country (flat or in the mountains) should figure in.
I tow roughly 10K in western NY, and honestly it is a joke to think I need a lower gear for even twice the weight.. When you read others say that you didn’t know that you were towing? It’s true..
That said, given what you may tow, the height of the trailer/wind resistance, the area of the country (flat or in the mountains) should figure in.
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