Truck - 2004 Ford F250 4x4 SD

Engine - 5.4L automatic w/ Over drive

Stock gear ratio - 3.73

New tire size - 37 Super Swampers

Question. I am torn between going with 4.56's and 4.88's. 4.56's would put me back to almost stock and 4.88's would be like having a 4.10 stock rear end. I do more around town driving and pull a trailer 3 days a week. Occasionaly, about twice a month, I pull a 24 foot boat.

What gear ratio would you all use and why?

What about fuel consumption?

Thanks

Doug D

 

If it were me, I'd go with the 4.88's. Fuel consumption probably won't be much different between the 2. Do you see any hills/mountains while towing? If so, definetely get the 4.88's.

Eric

 

I live in Florida - so not many hills here but I am just thinking that the extra umph may be good and allow the engiing to work better...

 

Go with the 4.88's. With that little girlie engine it should help a lot.. You will probably lose about 1-2 mpg, though.

 

Ha, ha---

Well the way the engine lugs now the milage couldn't be much worse. I average about 9.4mpg I would think that the 4.88's or the 4.56's would improve the milage...

Just a thought.

 

Wow, yeah. I can't see it getting too much worse. It should improve if anything.

 

I agree, go with the 4.88's, unless you are in the habit of driving 80+mph on the freeway. Your mileage while towing will probably be better with the 4.88's, plus more power. Unloaded mileage may be worse unless you slow down some.

 

if you have 265/75r16 tires stock. then 4.56's will get you to about 4.10's the 4.88's will be way low. i have 37's with 4.56's but i have the diesel engine. 4.88's would have been way to low.
jamie

 

265/75-16's are approx. 31.5" tall.

Using the formula: -------- NewGearRatio = (NewTireDia / OldTireDia) X OldGearRatio ------,

We can find the effect of different gear ratios and tire sizes and how they compare performance-wise with the stock ratio and stock size tires.

37 / 31.5 x 3.73 = 4.38. So 4.30's will get the effective ratio back to the stock 3.73 ratio.

For a 4.10 effective ratio, just plug in 4.10 for 3.73 in the same equation: 37 / 31.5 x 4.10 = 4.82. So 4.88's would be similar to a 4.10 ratio with stock tires.

If we plug in 3.90 for 3.73 in the equation: 37 / 31.5 x 3.90 = 4.58. So 4.56's would be similar to stock tires with a 3.90 ratio.

By the way, I run 4.56's with 33's on my gas-powered F350, for an approx 4.30 effective ratio .

 

Here is a sight with a gear ratio calculator
http://www.ring-pinion.com/calculato...latorsind.html

And true the 4.88's would be almost exactly like having a stock 4.10 rear end.

The end result will be about 200 rpm's more than what my stock 3.73 rear end produced.

Is 200 rpm that big a deal? I recently read an article in a truck mag that said that the factory ratios were generally to high and were for more general purpose. They recomended going lower if a person towed often or was mostly in town.

200 rpm higher than stock just doesn't seem like it will be that noticable.

 

FWIW - I vote 4.88's

It's there if you need it.

 

i vote 4.88

 

The 4.88's have it. They have been ordered from Precision Gear, I believe and will be installed next Friday...

I will let you know what I think after that...

Thanks
all..

Doug D

 

Sounds great! You made a good choice going with Precision too. Cost alot, but great stuff!

 

that is gonna be bad..gears are on my wish list
Siyé