Hey I wanted to do a gear swap on my SCab 5.4 4x4. It has 3.55 stock, and I want to up grade, but dont want to make my MPH worse. Should I leave it stock or go to 4.10's?


2003 SCab
FX4
5.4L
Cold air intake
Xcal 3 w/ VMP tunes coming soon.
Dual exhaust
18in wheels
285/60 Tires.

 

well the bigger gears you have the more "get up and go" your gonna have, but your mpg will get worse

 

not entirely true. you have a 31" tire so 4.10s will be more than enough with your current setup

what do you mean by MPH getting worse? you will be quicker off the line and be able to pull stuff from a stand still easier but your top speed will be slower (you will be able to do 90 instead of 95 if the change is that drastic).

if you decide to go with bigger tires (like 35s) then taller gears are a must and they may actually help your MPG in the long run.

 

HI!... I went from 3.55 to 4.10 gears and got better MPG on the highway and about the same as the 3.55's in the city. Was averaging about 21.3 MPG with 354RWH.P and with a 28 inch tall tire.

I'll be switching over to 4.10's in my 07 RANGER in a few weeks. It's currently got 3.55's, but needs a bit more low end grunt for towing.

 

i honestly think 4.10 gears are the best way to go for a truck. you'll gain much more torque.

 

He probably means that at any given speed the motor will be turning more RPMs - thus at any given speed over a given distance traveled more air/fuel will be used up.

So the taller tire increases the load on the motor and you can lessen that load again with a higher numerical gear ratio. But, there is a trade-off here. With physics, nothing is free.

Why not just keep stock tires and the 3.55s???

 

i assume you know that you have to do both axles, and that the job is in the ~$1500 range.

 

How much it costs depends on who is doing the job and which parts are being used. Do the job yourself and you will spend considerably less, all else being equal.

 

just did my 04 went from 3.73 to 4.10 got the gears and install kits from jaws gears for 750 bucks for both sets. mileage seems the same but it pulls alot better.

 

In my opnion ford geared the 97 -03 F150 to freaking high to get better gas mileage out of them. As far a top speed goes, how many F150 owners spend time driving there truck over 100 mph, I know I dont. I know troyer said this his intake, tuner, exhaust combo these trucks will do 140 mph so I know I have no desire to go that fast. But if you spend the majority of your time useing your truck as a truck ie: towing, carrying chit around I see no down side to gears. I plan on doing 4:10 soon my self.

 

140mph are you kidding me, i just put 265/75/16's on and just installed my hypertech max programmer and it goes go till 90 but after that forget it...

 

because the 3.55's make the truck seem gutless, hence using more fuel to get it up to speed and the engine works harder on hills

plenty of guys have switched to 4.10 gears and are glad they did so. I plan on swapping my 3.55 geared truck for 4.10's as soon as I can

 

I said STOCK TIRES and 3.55s......not bigger tires and 3.55s.

If you keep the stock tires and 3.55s the truck will burn less fuel and perform better than 4.10s and big tires. Stock tires may not be as much of an "ego booster" as the big tires, but they perform better on the street.

 

how do you go about changing your gears? ie where do you get the new gears, and do you need anything else besides the 2 sets of gears?

i can do the job myself, and i have a mechanic to help me, i have access to lifts and almost any hand/power tool you can think of.

 

It's not as easy as you appear to think it is. Setting up a rear end is a trade in itself......just like building engines and transmissions. Few "mechanics" actually do this and do it well. Installing a rear end, motor, tanny etc. is what most mechanics are equiped to do. Building them is another ball game.

I you have to ask...

"how do you go about changing your gears? ie where do you get the new gears, and do you need anything else besides the 2 sets of gears?"

...then, believe me, you can not do the job yourself, not without doing LOTS of research that is.

Installing the gears is the easy part, setting pinion depth and the carrier shims to get the backlash and wear pattern properly set that is the hard/time consuming part. If done right and without cutting corners, this is a very big job.