To go 3.21 or 3.92 on 35's? 90% of driving is at 55mph

r00st · Jan 23, 2017

I drive 75 miles round trip per day for my work commute. I plan to run 35's (can I run those with a level only or do I need a full lift?). My commute is a two lane 55mph road (usually going 55-60mph) with two stop signs. This should be fairly ideal for MPG, but im wondering if 3.21's are going to be geared too high for the cylinder deactivation to work? Will the 3.92's keep my RPM's too high to get decent highway MPG?

I know asking for high MPH on a lifted truck is silly, but I guess im just trying to maximize that figure, whatever it may be. With that said- does anyone have 35's with 3.92 or 3.21 to report on the highway mpg? My "highway" is different than what most people probably consider highway (75-80mph).

WilliamS · Jan 23, 2017

On 35's it seems on my 3.21 gears the cylinder deactivation kicks off around 74-75 mph is when I no longer see the eco light. If it is on its rare, anything under its fine and stays on. So at 70 mph on nearly the entire trip minus 2 overpasses it will stay in Eco. This is with my 2014 Hemi 4x4. If Im tame (70mph or less criuse) and this is 80% of my driving I will keep about 21mpg. When I step up to 75mph for the week and why I do that I will never know Ill average 18-19mpg.

DannyMK2 · Jan 24, 2017

given the opportunity, i would always go for 3.92's. cant think of any situation i would personally rather have 3.21's, especially with bigger tires. i suppose everybody's take on this is different though.

WilliamS · Jan 24, 2017

I will add, that if I find a salvage truck with the 3.92's I will upgrade. Terms of power and mpg the 3.21 I have no complaints, but theres always wanting more.

norville · Jan 25, 2017

I've never heard someone say "I just have too much torque at take off", or "this truck is just too quick off the line" If you have the option get the 3.92 or 4.10's of possible. I have zero regrets with 3.92 and I'm still on stockers..

crazykid1994 · Jan 25, 2017

My 3.92s matched up with the 8spd isn't a problem for the highway. 19mpg at 75 is what I see. Around 2000rpms if I remember right. My vw used to sit at 3300 at 75... and with 3.92s when I step up to 35s I'll still be alright.

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huntergreen · Jan 25, 2017

at 55 to 60 mph, the 3:92 wont hurt mpg as long as you dont mash the pedal to get up to speed.

Gump · Jan 25, 2017

3.92. I'm not a fan of 3.21s with any taller than stock tire.

To go 3.21 or 3.92 on 35's? 90% of driving is at 55mph

r00st

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