Here's the story. I've had my basically stock '05 CC 2wd 5.3 for about a year now. It has 3.73's and I find that when towing a 3000 lb trailer on flats ground, it's no problem. Going into the mountains, there are a lot of 6% - 7% grades, and while it doesn't have a problem pulling in 2nd, 3rd is just too high. I'd really like to have a 2 1/2 gear (fantasy).

I'm thinking of dropping in some 4.56's and with 31" tires, I don't think it would be all that bad. Most of my commute is 60 - 70 mph freeway though, and I'm a bit scared that my mileage will plunge. I also like the fact that it will be better for the occasional full throttle for fun stuff.

My question is in two parts - 1. How will mileage be affected, or rather how much, and 2. I will need t have a local (phoenix) shop do this, so what kind of cost should I expect, parts and labor?

Is $500- $600 in the ballpark?

Lastly, any problems I might run into like tranny issues?

 

I just installed 4.56's in my 4wd with an eaton for 1800 here in cali. Your price should be a good starting point. Im running 33" tires and i wouldnt want to go any smaller tire for cruisng on the highway. I love the way the power feels around town but on the highway i just gotta take it easy or the mileage goes down. But its not too bad around 65-70. Im still breakin em in but gears are the only way to go...

Matt