With increasing gas prices, and no end in site, I'm kind of reconsidering the 4.10's.

Here is my list of mods I what.

02’ PCM Swap and Wait4Me Custom Tune
Locker with GM 4.10 gears
MAC Cold Air Intake
Trans Cooler

I think the tune and intake will help maybe 2 mpg.

I have 3.42's now with a tall tire, 285/50/20, so my ratio is really like 3.15's.
If I change to 4.10's then my ratio would be around 3.90's.
Would this hurt my gas miledge?
I do most of my driving in townduring the week, but on the weekends I like to go out of town.

Also, should I get a locker or just change the gears? They cost so much. I want to be able to spin the tires. My truck dosen't have that many mods so it's pretty slow.

Thanks,
Nick

 

well i get about the same gas milage, but my driveing is town and hwy everyday, if you do alot of in town driveing then its going to help you out. Yes get the locker of some kind.

 

With those tires, your gas milage may go up. I had 35's on a truck with 3.42's, when I went to 4.56 I got better gas milage.

 

with my 3.42's and my motor almost stock i was getting 16city/20hwy. after i installed my 4.10's i was still getting 20mpg on hwy. now with the mods in my signature, my city driving has gone down to roughly 13mpg because of the stall and on the hwy i'm still getting 20mpg. also this is with a stock hight tire around 29.75" i'd say go for the 4.10's with an eaton posi

 

It really depends on how your driving is broken up (stop-and-go vs. highway, what speed/RPM, etc.) together with your driving habits.

If you spend a considerable amount of your time stoplight to stoplight, in town, and rarely go on the freeway (or let's say, less than 50% of the time), then you would probably do better with 4.10's than you would 3.42's. It takes less effort for your motor to get you vehicle's weight moving with 4.10's, and as a result, your truck would be more efficient.

If, however, you spend the majority of your time on the highway, and drive over 70-75 MPH, then you would likely get worse gas mileage with the 4.10's. This is my situation. I had 3.73's and swapped them out for 4.10's. Where before I got around 19 MPH on the freeway and 15-16 MPG overall, after the gear swap I got 16-17 MPG on the freeway and 13-14 overall.

An LS1-based motor is most efficient between 1800-2000 RPM's. At less than 1800 RPM's or so, the motor is not in it's power band and it struggles to move your vehicle's weight. Over 2000 RPM's and the engine loses efficiency - it spends more fuel to keep the same power applied to the drivetrain, and you lose mileage.

 

With those tires and wheels, get the 4.10's. I don't think you will notice a decrease in mileage. Possibly an increase under normal city driving.

 

mine stayed the same. if anything changed it was the city driving. i think it went up slightly.

 

i get about 23-24 city and about 18.5 hwy with mods in sig

 

Holy Crap! I guess you got your numbers backwards, but even so that's still incredible. I've never gotten 24 mpg, ever.

 

And you never will get even close, with 4.10's, unless you drive 55 mph.