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I have a 2017 F250 Diesel with 3.31. I am looking at towing a 5th wheel weighing in at 13328 dry and GVWR of 16670. If i do this, I'm thinking of upgrading gear ratio to 3.73, adding a leaf spring, new tires and air bags. I realize this doesn't change Ford's manufacturer's recommendations/guidelines but it basically turns my truck into an F350 with 3.73's. Has anyone done this or what are your thoughts?
Well Ford doesn't have a 3.73 option for diesel trucks. If you have 3.31 gears then you have the standard sterling axle, so you can find 3.73 gears if you want to do the swap.
. My‘15 had 3:73’s.
Anyway, my 5er is very close to yours in weight. I added bags and compressor to level the load, didn’t need the extra springs just for the trailer. I did change the shocks for Bilsteins. You may want to check the towing specs, if you haven’t already, to see if the gearing change is really needed. Little bit bigger project than bags and shocks. I would get higher rated tires than stock.
Welcome to the forum. Happy camping.
My thoughts: while your F250 will pull it ...
you are (unfortunately) another example where salesmen/ proud internet users have seriously led you astray.
To safely pull a (16K# +) load you need a 4.10 dually F350, with a GVWR rating of 14K.
To be somewhat within your current specs you shouldn't exceed (a carefully loaded) 10K pound fifth wheel.
I have a 2017 F250 Diesel with 3.31. I am looking at towing a 5th wheel weighing in at 13328 dry and GVWR of 16670. If i do this, I'm thinking of upgrading gear ratio to 3.73, adding a leaf spring, new tires and air bags. I realize this doesn't change Ford's manufacturer's recommendations/guidelines but it basically turns my truck into an F350 with 3.73's. Has anyone done this or what are your thoughts?
Tell us more about your truck. For example, what is the cab and bed configuration, and is it fitted with the optional High Capacity Trailer Tow Package?
The OP will gain nothing by changing gears other than spending money where not needed and thinking he'll gain more power to pull more weight. Here is the screen shot from the 2017 brochure...diesel 250s have the same gears as the 350s yet the 350s are rated for more and other than components added to carry more/ handle more weight so they're basically the same truck till "registration" time.
And here from the 2017 Super Duty sales brochure are the footnotes associated with some of the values shown in the chart above:
(1) Pickup box delete.
(2) Requires F-250 High-Capacity Trailer Tow Package.
(3) Gooseneck tow rating shown. 5th-wheel tow rating limited to 5th-wheel hitch rating of 18,000 lbs.
(4) Gooseneck tow rating shown. 5th-wheel tow rating limited to 5th-wheel hitch rating of 27,500 lbs.
A 5th wheel with a gross of 16670# will have a pin weight in the range of low 3000# to over 4000#. The OP will likely be over cargo carrying capacity before any cargo is added!
Pin weight is 2670. Cargo weight for my set up is 3450
Is that pin weight from a truck scale or sales brochure? If it's from the manufacturer it, like all other factory trailer specs is a mixture of guesstimating and fantasy, real world numbers are always higher than advertised for a number of reasons. My TT's advertised tongue weight is over 600 lbs lower than what it scales at loaded for camping with zero water onboard.
It sounds like a bigger truck or a smaller trailer would be a better option than what you have mentioned above.