Ford Super Duty Axle Ratios Explained
Ford Super Duty · Towing · 2027
Super Duty axle ratios explained: 3.31, 3.55, 3.73, 4.10 and 4.30
Which ratios each 2027 Super Duty offers, what each one does to towing, what the High-Capacity Axle Upgrade is, and how to read the codes, from Ford's 2027 towing guide.
Short answer
The short answer
A higher number (4.30) means more pulling power and higher tow ratings; a lower number (3.31) means a quieter, slightly thriftier highway cruise. For 2027:
- 7.3L gas: 3.73 or 4.30. Get 4.30 if you tow or plow.
- Diesel F-250 and F-350 SRW: 3.31 or 3.55. Get 3.55 for the top ratings; an F-250 also needs the High-Capacity Axle Upgrade (535) to tow over 18,200 lb conventional.
- Diesel F-350 dually: 3.55 or 4.10. Get 4.10 for heavy goosenecks.
- F-450: 4.30.
Availability
2027 axle ratios by model and engine
| Model | 7.3L gas | 6.7L HO diesel | Ratio behind the top rating |
|---|---|---|---|
| F-250 | 3.73, 4.30 | 3.31, 3.55 | Gas 4.30; diesel 3.55 with 535 |
| F-350 SRW | 3.73, 4.30 | 3.31, 3.55 | Gas 4.30; diesel 3.55 |
| F-350 DRW | 3.73, 4.30 | 3.55, 4.10 | Gas 4.30; diesel 4.10 |
| F-450 | Not offered | 4.30 | 4.30 |
From the 2027 towing guide's tables and ford.com maximum-rating footnotes.[1][2] Electronic-locking versions (3.55E, 3.73E) are offered on single-rear-wheel trucks.
Example
What the ratio does to an F-250's tow rating
| 2027 F-250 setup | GCWR | Max conventional towing |
|---|---|---|
| 7.3L gas, 3.73 | 23,500 lb | 17,300 lb |
| 7.3L gas, 4.30 | 26,000 lb | 18,200 lb |
| 6.7L HO diesel, 3.31 | 23,500 lb | 16,600 lb |
| 6.7L HO diesel, 3.55 with High-Capacity Axle (535) | 31,000 lb | 22,000 lb |
Ford 2027 Super Duty towing guide, F-250 SRW conventional towing table (highest value across cab and box configurations).[1] The diesel with a 3.31 axle tows less than the gas with a 4.30, so the ratio matters as much as the engine.
Top ratings
Top configurations by model
| Model and engine | Axle | GCWR | Max trailer |
|---|---|---|---|
| F-350 SRW, 7.3L gas | 4.30 | 29,000 lb | 19,500 lb conventional; 22,400 lb gooseneck |
| F-350 SRW, 6.7L HO diesel | 3.55 | 35,200 lb | 25,000 lb conventional; 27,600 lb gooseneck |
| F-350 DRW, 7.3L gas | 4.30 | 29,500 lb | 22,000 lb conventional; 22,500 lb gooseneck |
| F-350 DRW, 6.7L HO diesel | 4.10 | 45,600 lb | 28,000 lb conventional; 38,000 lb gooseneck |
| F-450, 6.7L HO diesel | 4.30 | 43,500–48,000 lb | 30,000 lb conventional; 40,000 lb gooseneck* |
ford.com 2027 F-350 and F-450 specifications.[2][3] *With the 40k Gooseneck Tow Package. GCWR is the most the truck, trailer, people and cargo can weigh together.
F-250 diesel
The F-250 High-Capacity Axle Upgrade (535)
What it does
Ford requires it for F-250 conventional towing over 18,200 lb, and it's behind the F-250 diesel's top ratings: 22,000 lb conventional and 23,000 lb gooseneck.[1][2]
What it costs
$1,130 on Ford's 2027 price list, for diesel F-250s. Ford takes $570 off when it's ordered with the Tremor package (code U10).[4]
Why it matters
Ford's towing guide warns that towing above 18,200 lb without it may void the New Vehicle Limited Warranty.[1]
Or step up to an F-350
An F-350 SRW diesel is rated higher out of the box, for about $1,300 more than an F-250 at the same trim. F-250 vs F-350
Reading the sticker
Ford axle codes
| Ratio | Open | Limited slip | Electronic locking |
|---|---|---|---|
| 3.31 | 31 | – | 3H |
| 3.55 | 35 | 3K | 3J |
| 3.73 | 37 | 3L | 3E |
| 4.10 | – | 4N | – |
| 4.30 | – | 4L | 4M |
Ford 2027 Super Duty towing guide.[1] The code also appears on the Safety Compliance Certification label in the driver's door jamb. All Super Duty order codes
Up north
Picking a ratio for Barron-area driving
Plow trucks
A gas 4.30 with an electronic locker gives the most pushing power at low speed and the locker helps on icy driveways.
Campers and boats on US 53
A diesel 3.55 handles most campers at highway speed. Choose 4.10 on a dually if the trailer is heavy.
Mostly empty commuting
A 3.73 gas or 3.31 diesel runs quieter at 65 mph. Just know the tow rating drops.
Tow and payload figures are Ford maximums for a properly equipped truck. Your truck’s actual limits depend on cab, bed, axle, engine and options — confirm with Ford’s 2027 Super Duty towing guide and the door-jamb label before you hitch up.
Frequently asked questions
What axle ratio should I get on a gas Super Duty?
For towing or plowing, 4.30. On a 2027 F-250 it raises the conventional tow rating from 17,300 lb (3.73) to 18,200 lb, and it's the ratio behind the gas F-350's top ratings. Choose 3.73 if the truck mostly runs empty on the highway.
What axle ratio should I get on a diesel Super Duty?
On an F-250 or F-350 single rear wheel, 3.55 carries the top tow ratings; 3.31 is the quieter highway ratio with lower ratings (16,600 lb conventional on a 2027 F-250). On an F-350 dually, 4.10 unlocks the 38,000-lb gooseneck rating. The F-450 uses 4.30.
What is the F-250 High-Capacity Axle Upgrade Package (535)?
A $1,130 package on diesel F-250s that Ford requires for conventional towing above 18,200 lb. With it, the 2027 F-250 diesel is rated up to 22,000 lb conventional and 23,000 lb gooseneck. Ford warns that towing above that level without it may void the New Vehicle Limited Warranty.
What does the E in 3.55E or 3.73E mean?
It's an electronic-locking rear axle. Pushing a button locks both rear wheels together for deep snow, mud or a slick boat ramp. Ford's order codes are 3H (3.31), 3J (3.55) and 3E (3.73) for electronic locking.
Does a lower axle ratio save fuel?
Usually a little, because the engine turns slower on the highway. The difference matters less than how heavy you tow and how fast you drive, and heavy-duty pickups have no EPA mpg ratings to compare.
Where do I find the axle ratio on a Super Duty?
On the window sticker it's on its own option line, such as "Electronic-Locking w/3.55 Axle Ratio". On a truck you already own, the code is on the Safety Compliance Certification label on the driver's door jamb.
Can I change the axle ratio after I buy?
Only by replacing the gears in the axle, which is expensive, and it doesn't change Ford's official ratings on the label. Order the right ratio from the factory.
Two stores, one street
Talk with a Super Duty specialist in Barron
Tell us what you tow, and we will find a truck with the right axle or order one. Call ahead and we will have the vehicle pulled up, warmed up and priced out the door.
Swant Graber Ford
1697 East Division Avenue, Barron, WI 54812
715-537-9500
Swant Graber Motors
Chevrolet · Dodge · Ram
1690 East Division Avenue, Barron, WI 54812
715-537-5657
More Super Duty guides
- Ford Super Duty Buyer's Guide (2026–2027)
- F-250 vs F-350 vs F-450: which one do you need?
- 7.3L gas vs 6.7L High Output diesel
- Super Duty order codes explained (600A–773A)
- Fifth-wheel and gooseneck towing setup
- 2027 Super Duty Carhartt Package
- Super Duty trims and packages, explained
- 360° camera, XL Driver Assist and XLT Premium
- Ford towing and work packages: worth it?
- Camper and snowplow/camper packages
- Super Duty appearance packages
- Tremor Off-Road Package explained
- Super Duty maintenance schedule
- Used Super Duty recalls by year
- Super Duty Chassis Cab guide
- Shop new Super Duty in Barron
Get the right axle the first time
Shop Super Duty in stock by axle ratio, or factory-order the exact setup. We work with national and local lenders.
Sources
- Ford, 2027 Super Duty Pickup Towing Guide: axle codes, F-250 towing tables, 535 requirement: ford.com
- Ford, 2027 F-250 and F-350 specifications and maximum-rating configurations: F-250, F-350 (ford.com)
- Ford, 2027 F-450 specifications: ford.com
- Ford, 2027 Super Duty price list (price level 720, 09/17/26)
Updated October 30, 2026. Specs, package content and prices are subject to change by Ford. The window sticker and door-jamb labels on the vehicle are final. Not affiliated with or endorsed by Ford Motor Company.