February 24, 2008i have stock 3.92 gears and running stock 20in rims with 35in tires. how would my MPG be effected by changing to 4.56? The drop in performance doesnt kill me but the gas sure does. I dont know what i get know b/c my speedo and computer are all off. how do i fix that?
February 25, 20083.92 not bad, but go to 4.10 or 4.56 would be better for 35's
You need a programmer to fix speedo for bigger tires.
February 25, 2008I would definietly go with the 4.56 because if you go over 35's it will be the best way to save some of your MPG's. Superchips allows you to recalibrate your speedo. I'm sure theres other ones also.
February 25, 2008The 4.10' won't make much of a difference, the 4.56 will get you closer to stock performance/gas mileage.
February 25, 2008-Stupid 456 gears and some kind of programmer is the way to go
February 25, 2008What Sierra Ram said. With the 3.92's your engine will be lugging and will be behind the power band. The 4.56 will put it back in the sweet spot therefore giving you better fuel economy.
February 25, 2008I deffinately would if you want stock power and fuel mileage back.
Theres a website out there that has an informational graph that will tell you what gears to install in accordance to what size tires you are using but I cant rember where I saw it. Its pretty useful, tho. It tells you how far you can go with stock gears in either direction up to a certain difference in tire sizes before it crosses the threshhold on whats acceptable and whats not recommended.
Also, if you dont want a combination power programmer/speedo calibrator, Superlift makes a speedo calibrator just for correcting speedos due to tire and gear upgrades called the Truspeed. Good thing about it is you can put the correction right where you want it rather than just telling it what size tires and gears you have. Plus it has 2 settings for two seperate calibration settings. It hooks up inline to the whel-speed sensor and uses a tiny screw and by turning it one way speeds up the speedo and turning it in the other direction slows it down.
February 25, 2008alright thanks guys. so it seems like 4.56 gears will make my MPG much better. Any suggestions of website to purchase from , how much is installation costs. Is it okay to purchase used ones?
February 25, 2008Egh, something like this Id rather use new parts since gears are a integral part of your drivetrain and when its comes to used parts, you wont know the history of behind them unless you know the person yer buyin from. Id hate for ya to by some used gears that were used pretty hard then failed on ya causing more headaches and money. Im not sayin that will deffinately happen, but its not a risk I would take.
February 26, 2008I am running 36's, with 17in rims. I noticed a big drop in power and MPG. I haven't done the gears yet, but I did intake, chip and exhaust, and noticed a small change in HP and MPG. I think with everybody's post, I will change to 4.56's instead of 4.10's.
Thanks everyone for posting.