I tried to find the original post but couldn't find it but:
After changing from 3.55:1 to 4.10:1 ring and pinion gears my gas mileage actually increased by about 2 mpg. That is for all city driving. That was a nice surprise in addition to the expected increase in performance(acceleration).

 

Did you change the gears yourself or did a shop did it for you??

 

A transmission shop did it for me.

 

where'd you get the gears and how much for everything?

 

OK...so..what kind of mileage are you getting?

 

That is not uncommon at all. Since you need less throttle to achieve the same rpms from a stop you'll use less gas.

I went from 3.92s to 4.56s and saw about a 2 mpg increase in town, about the same on country roads and dropped about 1 mpg on the interstates where I am cruising at 75 mph'ish...

 

now i wanna know if your always in the throttle how much does it drop then over what you had stock?

 

The gears, bearing kit and LSD cost $607, install was $295. Since I wanted the installation shop to give me a warranty, I got the gears and LSD from their recomended supplier (Dallas Differential). My city mileage average is 16.68 now, includes some hard acceleration since this was the first tank of gas and I wanted to play a little.

 

okay well not bad for all that for a grand including install! very nice man!

 

my install was 1600.00 back in 05, but mine is a 4 x 4, you will be amazed at what a simple swap will do, especially for the 6 cyl trucks