Gear ratio Q's

[TXKID]

Ok everyone now bear with me on this... My understanding is that a lower gear ratio will get me off the line faster and vice versa with a higher gear ratio so my thinking led me to the theory that a lower gear ratio might help improve gas mileage in the city or at lower speeds (if you don't try and blow up your tires at every stop light) since its able to turn the wheels easier.... How reasonable is this?

And also if you have made the swap can you post your gas mileage before/after and what gears you have now and what you went from? Also if your currently running 3.92's with a lift can you post up your current mileage?

I'm currently trying to decide between the 3.92 or the 4.56 bc these current gears are just not cutting it, but I also don't want my gas mileage going down too much since its already horribly low and I make two hour round trips every couple weeks on top of my daily driving.

Any help would be greatly appreciated

 

[BlackedOutHemi]

I'm assuming you have the 3.55 now? Since you're a 2012 I believe the swap to 4.56 is impossible without swapping the front axle for a 2009-10 since the gears are welded in. That might get a little pricey. But you'll have to do that for any gear swap anyways, and I don't think jumping to 3.92 is enough if you're gonna go ahead and do it.

Honestly, I'd do 4.10s if I were you. Little more umph than the 3.92 gears but not so low that they hurt MPGs on the highway too badly. I know with my 4.56 in my last truck, anything over 70 was pushing it as I was up into the 2200s in RPMs.

As for your theory. That's something I've thought about to and I believe it would be true. So your city MPGs should go
Up while your highway will go down from higher revs.

 

[Bigboytoys]

Agree with Eddie on this. Looking at your sig, you are turning 37s with 3.55s (I am assuming here) there lies your biggest problem....trying to turn big meats with 3.55s....I would definately skip the 3.92s and go straight to 4.10s.

 

[AV8B6015]

I'm thinking the same thing. I have the 3.55 and I'm running 35's. My buddy has a 2012 with 3.92, and he gets about 2 mpg's better than I do. I had been thinking about the 4.56 swap, but as I understand it, that's not easy on the 2011's, so I may just do the 4.10 swap at some point.

 

[Graygoose]

Yes, adding lower gears CAN help mileage AND around town. no lugging the engine. I had a Yukon, 4.8, 20's and 285/50/20's...came stock with 3.42 and G80. So I added Yukon 4.11's and it helped power alot, and helped mileage.

 

[TXKID]

Does anyone know where I can get the 4.10's for my front carrier?

 

[BlackedOutHemi]

It'll have to be done by swapping the front axle out and then putting aftermarket 4.10s in there. There are no factory 4.10s for the front because RTs are only 2wd.

 

[09SMOKINHEMI]

might hit up Matt from Moe's Performance to see if he knows of anyone who would be able to swap out your axle and make it work

 

[Sideshow]

I've talked to Matt and others about changing the 2012 gearing.
For the front, you will need to get a new carrier from a 2010-11 to work.
fastNugly is the only one I know that's done it.
The rear carrier bolt pattern can be modified or you can swap in a 4.10 setup from a RT.
Either way it's not a cheap mod for us 2012 guys.

 

[TXKID]

Yea I've been looking into this for a couple months now and probably won't happen til summer