Breakdown of Different Gear Options/Ratios for super duties - Ford Powerstroke Diesel Forum
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post #1 of 30 Old 12-22-2011, 10:39 AM Thread Starter
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Breakdown of Different Gear Options/Ratios for super duties

Hi Guys,

Can someone breakdown and explain the different gearing options for the super duties including best use scenario, mileage, top speed, torque, etc.?
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post #2 of 30 Old 12-22-2011, 02:59 PM
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The gear ratios for the Ford Super Duty trucks are 3.31, 3.55, 3.73, 4.10, 4.30. I am not absoutely sure of the 4.10/4.11, but is has been a good and common ratio for ever.

The smaller the number, the better the mileage with these diesels. The bigger the number, the more that the truck will pull. The axle ratio choices are vast because of the vast use of the vehicles they are put into. The F250 and the F350 non dually can have the 3.31 gears. The dually can get the 3.73, but not sure if the 3.55's are available. The F450 only gets the 4.30 gears.

I guess the real question is what will you be doing with your truck?
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post #3 of 30 Old 12-22-2011, 03:12 PM
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The two common are 3.73:1 and 4.10:

3.73:1 is 3.73 revolutions of the driveshaft to 1 turn of the ring gear.

4.10:1 is 4.10 revolutions of the driveshaft to 1 turn of the ring gear.


There are limited slip differentials, open differentials and locked differentials.

These are the common rear axles for the super duties from 99-03. After that I am not sure what was offered because I own an 02.

Now depending on tire size, driving conditions and all that. The lower the gear ratio the better fuel mileage you will get.

The higher gear ratio the quicker acceleration you get but lower fuel mileage.

As for fuel economy you want a lower gear ratio. This will keep your rpm's down, for top speed well they will all have the same top speed just depends on how quick you want to reach it.


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post #4 of 30 Old 12-23-2011, 12:58 AM
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those are the old ratios. The SRW have newer rearend ratios.

This is a hugely misunderstood topic.
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post #5 of 30 Old 12-23-2011, 05:46 AM
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For the new 6.7L trucks with a single rear wheel(SRW) you have the choice of 3.31 gears or 3.55 gears.

For dual rear wheel f-350's you can get 3.73's gears

F-450's come with 4.30 gears.


The point of gearing is to find a happy medium between fuel milage and towing power(torque).

The lower number gears such as a 3.31 will net you better fuel milage because the drive shaft turns 3.31 times for each turn of the tires vs something like a 4.30 gear which the drive shaft will turn 4.30 times for each time the wheels make a rotation. Thus with the 3.31 gears the engine will be turning at a lower RPM at the same mph vs the 4.30 gears.

On the other hand a 4.30 gear will increase torque to the rear wheels for starting off with very heavy weights. The truck will have a much easier time being able to pull a heavy load such as 25K lbs than a truck with a 3.31 ratio

The trick is finding which is the best combo for what you plan on doing. Most guys will not need the 4.xx gears with the power that these new trucks make

Hope this helps if not try reading up here
HowStuffWorks "How Gear Ratios Work"
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post #6 of 30 Old 12-24-2011, 04:44 PM
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Quote:
Originally Posted by knotcher View Post
those are the old ratios. The SRW have newer rearend ratios.

This is a hugely misunderstood topic.
What They listed is Correct except the 4.10 I don't see it listed.....

For 2010/11/12 You have:

3.31
3.55
3.73
4.30

3.31 and 3.55 are for F250/350 SRW ONLY!

3.73 and 4.30 you can get in DRW OR Gasser

If you Don't pull much the 3.31 is the way to Go...

IF you tow or Plan to lift the truck i would go with the 3.55's

You will loose around 3 to 4 MPG when you lift it,before you even ask This is Stock! you can mod it with the Deletes and H&S Tunner and get some of this back even more in some cases Your truck will very as No two trucks are the same!
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post #7 of 30 Old 03-21-2013, 06:40 PM
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my 97 gasser has 4.10 gears i know it does since had to replace the axle after i snaped it pulling trees out of ditch
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post #8 of 30 Old 03-21-2013, 06:45 PM
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Quote:
Originally Posted by mogle View Post
my 97 gasser has 4.10 gears i know it does since had to replace the axle after i snaped it pulling trees out of ditch
Entirely possible, but the 2011+ trucks are different.
though.

Btw, very old thread.



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post #9 of 30 Old 03-21-2013, 09:12 PM
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Quote:
Originally Posted by mogle View Post
my 97 gasser has 4.10 gears i know it does since had to replace the axle after i snaped it pulling trees out of ditch
Holy thread revival! Good job FNG..

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post #10 of 30 Old 09-05-2013, 10:50 AM
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I have a question...
I have a 2013 F-350 diesel 4X4 that came with a 3.31 differential.
I have the 6 speed auto transmission.
WHY in 6th gear letting the transmission do it's own downshifting when needed I get 15.5 MPG (not towing). When I lock the transmission in 5th gear going over the same 150 mile round trip I get 17.7 MPG.
When pulling my 5th wheel trailer letting the transmission do it's own thing I get 9/10 MPG. With my old 2006 F-350 diesel 4X4 5 speed 3.72 gears pulling the same trailer over the same 5,000 mile round trip I would get 10/11 MPG.
Also the 2006 would get 15/16 MPG non towing.
I feel the 2013 is geared to high, also I have noticed that the 6 speed does not respond very well to down shifting and it seems to load down the engine before a down shift. When it does downshift it will go to 4th gear, going like a bat out of hell then when I let up to goes right back to 6th gear.
Ford (dealer) is no help because of no computer error telling that there is something wrong. Also I was told if I change the gear it will void my warranty.
Nothing but a bunch of BS from Ford just like the 06 diesel.
Any ideas on what gears to install? I'm thinking about 3.55 but also wondering about the 3.73 because the 06 had that gear.
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