I am trying to get better fuel mileage, would there be a reason not to replace my 4.10 rear end gears with something like 3.73 or something equivelant?...

it depends on your current wheel and tires size set up

It's all stock.

you will get better millage on the highway but will lose some in the city
its a catch 22 deal

What about low end power?

You do have a 2wd, right?

You'll see a slight decrease in low end power. How noticeable it would be would depend on your driving habits.

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ɹǝʌo ǝɯ dılɟ

No its a 4wd.

than the answer to your post is no

you would have to do both the transfer case and rear at the same time
and the cost for gears to fuel would not be justified

Right, you can't change just one set of gears. Front and rear of a 4wd must be done together.

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ɹǝʌo ǝɯ dılɟ

on a 4wd, you don't want anything geared higher than 4.10 IMO. And as said before, you can't just change the rear...gotta change the front gear as well...gotta have them matched unless you wanna lose your 4x4-ability by removing your front shaft. Running different gears front to rear would cause the transfer case to bind inside. My buddy's chevy had 4.11 in the front and 3.73 in the rear and we'd wheel it....took 1/4 mile in reverse to unbind the tcase. Wasn't good on the tcase at all.

Notice how the thread jumped around a bit, Jason? Please create yourself a signature with some info about your truck. It'll help us help you alot better and faster. Year, 2wd or 4wd, engine, trans, mods, etc.

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'01 XLT disguised as a '03 Fx4 Level II.