I'm stickin 4.56s in my truck to replace the 3.55s...i know this sounds stupid, but will i be able to tow more than i was able to? Or will it just be easier?

Stupid question, but i'm not a gear head in differentials really...know what they are and how they work...

 

Yes, and Yes.

You can pull a boxcar with a Briggs & Stratten if you gear it properly.

Changing final drive ratio (aka: the 'rear end') changes several things, among which include:

a) it increases the mechanical leverage (torque) available at the drive wheels.

b) it raises the engine RPM for a given speed. This is not intuitive, but at, say, your chosen towing speed, the engine is making more HP than it did. So, not only have you increased the leverage by way of changed gearing, you have moved your engine higher into the power band.

For example: 2000 RPM for a typical (mine at 70 MPH in OD) 5.4L is around 123 HP; and at 2100 RPM (the difference going from 3.55 to 3.73), the HP is around 129 (a 5% increase) -- while the torque at 2000 is 330 lb Ft; and at 2100 RPM it is around 335 lb Ft (for less than 2% increase).

The difference is profound when making a more significant ratio change like:

3.55 vs 4.56:

2000 RPM becomes 2570 RPM (and 123 HP becomes 160 HP, respectively - Up 30%); and 330 lb Ft becomes 350 lb Ft (up 6% and at max torque for the engine).

Note: The above illustrates how going from OD to Direct makes such a difference. The 2000 becomes 2800, and 123 HP becomes 175 HP (@ 335 lb Ft), respectively -- Noticeable by anyone's Buttometer due to the 42% increase in HP!

c) moves the torque band lower in the speed range.

d) turns your water pump and fan faster

e) Increases your alternator output for a given road speed.

f) Decreases the load on the engine/transmission for a given load and speed (due to the torque leverage).

g) Increases final drive pinion wear (smaller pinion = greater RPM and sliding on ring gear).

h) Lowers the maximum safe driveshaft (road) speed.

i) Places additional load on the gear lubricant.

j) Increases the effect of engine braking

k) puts a smile on your face when you hit the accelerator.

 

Changing your gearing will increase your tow capacity, but the larger than stock tires that are on your truck will reduce it. You will have to do the math to figure out if the "net" change in gearing will add to your tow capacity.

 

The other thing to remember is even though you have increased the towing power of your truck, the GCWR is unchanged. Only Ford can change that. If you are over your GCWR and get in an accident, you may be liable.

Ian

 

I had assumed you had changed gears already?? Those big tires have definitely robbed you of some low end power to begin with! With 4:10's you could be back to stock acceleration, 4:56's maybe a little more. I'd do it if I were you, in fact I'm staying close to stock diameter and installing 4:10's sometime this year.,,,,98

 

Someone post that gear calculator, I have no idea what site it's at,,,98

 

theres one at super swampers website, intercotire.com. I have already ordered the gears, but they have not yet been installed...still waiting on them to get here

 

Stupid question, but? You ordered a set for both axles, right?,,,,98

 

yup. I know quite a bit about gearing actually...what i really shouldve asked was that, although i'll have more torque, will my axles, etc, be able to handle more...i know the engine will find it easier, its more a matter of if its equipped...

but yes, both axles...and reverse cut for the front 8.8 too...

 

Had to ask, you know,,,,98

 

Where did you order the gears from, what are the part numbers, and lastly, what did you pay for the front and rear? Just thinking about it. Thanks!

 

Nope, it will NOT increase your towing capicty

Yes it will make it easier, especially at launch and when climbing hills.

 

I agree with Petrol. It will NOT increase your towing capicty, but will make it easier when taking off and climbing hills. The MAJOR items in your truck that determine what your towing capicty of your truck are is "Engine and Trans combination" without changing that combination your towing and hauling capicity remain the same. Of course there are other items as well, suspension, brakes etc. but the Engine and Trans are the main ones. Try to tow more then its rated for and you may find that you will cause damage to one or both of them. You can gear all you want but the fact remains the towing capicity is related to the complete truck not just the gears.

 

Thanks all of yall, I figured that I was pretty much limited by the equipment...but the gears should make it easier...

But thanks again...

 

Nevermind