I had a question about switching to a higher gear ratio. I know about the benefits and drawbacks, but when you switch from 3.92 to 4.56, do you need to do any other mods? Obviously you'd need the speedometer recalibrated, but is there anything else? Or is it jus a matter of swapping the old gears out?

Any advice from fellow Hemi owners would be appreciated. I have a 4x4 so I know they need to change the front as well, but I want to know everything I can before I have it done. Thanks.

 

Nothing is needed. There is a ring speed sensor in your rear housing that will pick up the gear change. Your speedo will auto adjust. Nothing else is needed for the rear change. Gears and a full bearing kit. You'll need some limited slip additive if you have LS. Having the 3.92's, you won't need a new carrier up front.

 

Just so you don't get corrected by a mechanic - numerically higher gears are called a lower gear ratio. Numerically lower gears are called a higher gear ratio. I think you will be very happy with the 4.56's.
Just buy a kit and go to a small garage. It should not be more than $400 or $500, if it is then shop around. IMO, go ahead and install a locker as well something like the Power Trax. The reason I say use a mechanic is because backlash settings are very important and hard to set for the inexperienced.

 

Well I am running 4.56 and I love them and they are a great gear in my opinion! But I am running 40 inch tires...

 

Im running hte 4.56's and have had them in for a couple years.... I absolutly feel they should be the FIRST mod on ANY 3rd Gen Ram. They have increase my fuel economey up to 65MPH and make drivng such a heavy truck FUN. Im running the shorter 17's at this time with a tire hight of 29.75" tall....

SPEED SAFE, AIR RAM

 

AND my top end is well over the 120MPH you see on the speedo... I would guess it to be more like "L1" ... or 140+MPH when I let off the gas... it was still pulling hard at the "L1" mark... (LOW 1 on your shifter indicator)

SPEED SAFE, AIR RAM

 

Will replacing the stock gears with 4.56's void the powertrain or bumper to bumper warranty?

 

Probably evey state is different but if there is a warranty claim, the dealership has to prove the mod is what caused the problem before it can be rejected. Of course that's like the myth of innocent until proven guilty. It's more like you have to raise hell that the mod didn't cause the claim.
If it's really a comcern, have the dealership install them for you but as I was told on putting a lift on my Jeep, as long as it is done professionally, it will be easier to claim warranty. Just keep your receipts.

 

what are the benefits of switching to 4.56? Ive got a 3/4 ton, and it has trouble running at over 70mph, the rpms are always jumping around.

 

does a 4.56 gear ratio improve your mpg? i would have thought it would decrease it.