Small rear diff swap

[Carlos DaSilva]

Hi Ram gurus. This is my first post.
I have a 2003 Ram 4x4 with a 4.7 engine and 3.21 differential. My question is I would like to change my differentials to a 3.55. Is this possible without replacing the entire casing and shafts. Is it worth it? I'm trying to get a little more power from this 4.7L and a little better gas mileage that is only 12.5 per gallon max. I don't beat on the truck.

 

[Karlsweg]

In my opinion not worth it. What you would pay to do it would take years to offset any mpg gain. And that’s assuming a .34 change would net any. “Power” wise you probably would have to go to a 3.92 but then you lose any mpg gain on the highway but city may improve. Just my 2 cents worth.

 

[Travelin Ram]

Financially that kind of thing will never work out. This from someone (me) who spent way too much time and money upgrading a 2004 Jeep.

Like most performance mods, it’s a labor of love. Or lust maybe.

With a vehicle that age, unless it has some special meaning to you, I’d advise spending that money toward trading the truck for one that’s already set up to perform the way you want.

The 4.7 is known to be a short lived engine, which would deter me from any investment.