Cowboy Tom

I've got a 2008 Silverado 1500 5.3L 4L60E 2WD with factory 3.42 gears, ext cab std bed. its still basically stock right now, I think the first thing I'm gonna do is gears, I've been debating between 4.30's or 4.10's I think i'm gonna go with 4.10's, I looked at gears for a while, and I've talked to people before.

I just wanted to get a little more info before I do it, I mainly wanted to heard from people who have 4.10's and what kind of fuel economy should I expect??

also I currently have 31's but I'm gonna run 33" A/T's (285/70R17)

Thanks for any help or info

bobfig

Imo opt to get come locker so you wont have the g80 in there.

Im thinking if you are going with 33" tires go 4.30 or 4.56 as it would be more fun. Find a calculator online to see what you would be spinning rpm wise. Would aim for 2200rpms at 70 would be best.

Cowboy Tom

Right now factory setup I run right at 2000RPM at 80MPH, and just below 1800RPM @ 70MPH, of course I know I'm gonna run higher RPM but do I really want it that much higher?
Also I have thought about a new locker or LSD with the gears, is there one you recommend, price is a big factor for me

Cowboy Tom

My plans for the truck is just gears, built transmission, and only bolt-on's with the engine

bobfig

im at 2000rpms at 70mph but with bigger tires tend to add a few more to overcome the weight of the tire.

i finely got home after a long day to put the numbers in and at 70mph are:

4.10 and 31" tires = 2173rpms
4.10 and 33" tires = 2065rpm

4.30 and 31" tires = 2279rpms
4.30 and 33" tires = 2165rpms

Cowboy Tom

What kind of MPG do u get? And what's ur gear and tire size?
I have a RPM calculator app on my phone, in my equations I used 32.78" as tire size, (285/70R17 is 32.8") and .70 for transmission ratio, .70 is 4th gear right?

GMCtrk

iTrader: (27)

My experience...YMMV:

3.42s ....23 mpg
4.10s ....18 mpg

All other factors held equivalent

Cowboy Tom

I've got 3.42's factory and have never made over 20.5mpg hwy, and that was with cruise control on like 65mph (yes, that was under the speed limit)
Cruise control set about 80mph equals 17.0mpg

bobfig

Well, befor the heads i would get like 17-18 highway at 70 and 14-15 mixed. But now after the new heads im only getting like 12-13 city. Im probably still need more work on my tune bit everyrhimg seems to run fine.

KyleW707

I've got 4.56's in my 08 crew cab 4x4 with 35's and 6 inch lift and 180k miles. I average 14mpg whether it's in town or my occasional 700 mile round trip at 75mph, with hilly terrain. I also have longtubes, cai, and a tune. At 75mph I run about 2300-2400 rpm. Seeing as your truck is lighter, higher gear, and smaller tire, I'd expect you'd see a solid 2-3mpgs better than me.