Hey guys, I will be switching to 4.56s pretty quick here. I was wondering if this would throw my speedometer off. How much will it be thrown off? Can the dealer readjust it for me? Should I do that with a programmer? Thanks for your help.

 

If he or I did that mod what could we expect our top speed to drop down too. I think I have 3.73 of 3.55 gotta check. I have an STX if anyone knows

 

You have 3.55s. I'm not worried about top speed!

 

I am a little worried. Whenever I am driving home from school I usually cruise at 90 maybe a lil faster assuming that it clear stretch. Anyways so what do you think. Would the difference be night and day?

 

Im pretty sure you could still hit the governor.

 

From what I understand the OD on the truck is huge so with 4.56s you are still well over 100 mph before redline.

 

ok i guess i should be okay it is not like i street race. i just like to get places faster. Anyways so would the differences be night and day? I can chrip the tires and that is about it.

 

Your speedo WILL read much faster than you are actually going.
Yes. Your dealer CAN fix this for a price. I think someone said $35.

Why not go ahead and search Ebay and drop a couple hundred on a tuner and fix it yourself? SuperChips MAX Micro Tuners usually go for around $200 now-a-days

EDIT: This is a gues, but I would expect your speedo to read about 12-15 MPH fast. Mine ran about 10 fast when I changed to 4.10's.. with a 1" smaller tire than you got.

 

Okay so what other differences would I notice? Gas mileage? Noise? Power by the butt dyno?

 

You really need to search this better on the internet... but.

You will notice faster acceleration. You DONT gain any horsepower, but you apply the power that already there to the ground.
You WILL notice a decrease in gas mileage. Prolly around 2-3 MPG less.
Noise... the gears will make a little more noise than the stock set does... Mine dont make much more noise than the stockers, but if I listen REAL hard, I can hear them buzzing/whining.

This is NOT a mod you can do yourself. It is expensive, and for how much you pay for the gears/install, I'd say its permanent too.

Do a google search for "gear swap/ changing to 4.56 ring and pinion".. stuff like that.

 

I understand the whole concept and the expensiveness. So I will definitely notice a big loss in MPG?! Son of GUN! I don't think I can afford to loose more gas

 

Maybe I should take that back... maybe just a 1 MPG drop... you already run 33's.

Its a truck. It wasnt made to get good gas milage. When ever you get the mentality of "Screw gas milage", let the mods begin! Sooner or later, you have to. YOur not driving a car...

With that said, I still get about 18-19 MPG on the highway with 4.10's...

 

Let me ask you this do you have LFS? (Lead Foot Syndrome) Cuz that will kill your mpg too

 

I have 4.10' gears, an air intake, custom exhaust, a dyno tuned Xcal2, and underdrive pullies...

I'll let you answer that question for yourself..

 

I have 4.56's and a 5.4L with 33's.... It will cost you 1.5mpg highway and give you lots of acceleration gain across the board. As khendrix said you will have to see the dealer or get a programmer for your speedo adjustment. Runs 2050 rpm at 60 so roughly 3420 rpm at 100 mph. I beleive the 3.73 runs around 1650 at 60 and 2750 at 100 mph. You can hear the gears whine especially when slowing or coasting. Sounds like a supercharger whine but much quieter.