Differential gear vs tires size

[lucky RAM]

Hi everyone, my name is Luc and I'm new in this forum. Sorry if I make some mistakes when I'm writing, I'm french but I will do my best.

Here is my question :

I saw many posts and pics with a 6'' lift kit and 37'' inch tires and I want to lift mine. But do you need to change the gear ratio in the diff ??

I have a 2014, 1500 Hemi 5.7 with 3.92 gear ratio right now.

Thanks for your answers !

 

[Andy578]

you should be good with 3.92s

 

[R.L.K.]

Lucky french Basterd ! LOL !
You've got 3.92s !
Like stated ed above sir , you should be fine .
I'm assuming you have the 6 speed xsmn ?
If you feel your performance drops too much with 3.92s & 37s you could regear to 4.56 , but it is costly and extensive , likely your performance gain would be better to spend your money on performance mods not gears.

 

[powderbrad]

You be fine. Though...I wouldn't mind a 4.10 gear in my truck for fun.

If I had 37s....I might consider 4.56. But with the 8spd likeley go FORCED AIR

 

[Rzrman328]

Welcome.

3.92's and 37's will work completley fine.

Absolutely No need to swap gears.

 

[Andy578]

If you feel your performance drops too much with 3.92s & 37s you could regear to 4.56 , but it is costly and extensive , likely your performance gain would be better to spend your money on performance mods not gears.

depends if he has 4x4 or not. forget the prices i've seen now but it's nothing crazy to swap out on a 2WD

 

[R.L.K.]

Lol I always assume people who plan on lift & 37s are 4wd . My bad .

 

[Rzrman328]

Lol I always assume people who plan on lift & 37s are 4wd . My bad .

Usually a safe bet.

But then there are those guys

 

[Izzyb47]

Gear mpg highway vs city

I keep seeing people say they lose Mpgs on highway when the regear but gain at slower speeds why would that be the case if your making you ratio to the tires closer to factory? I have a 3rd gen 6" lift with 37s and I'm rehearing to 4.56 does that have anything to do with changing the tire size via tuner. It would seem to me logically that the pcm would read speed separately from the shift points and the shifting would be controlled by tachometer

 

[Etroze86]

Friction of air and riding so high is a big reason for loosing mileage, another reason is the mass of those heavy ass 37" tires. Shifting isn't necessarily controlled by tach but a combination of speed, RPM and line pressure in the transmission if that makes sense.

 

[HammerHead]

Hi everyone, my name is Luc and I'm new in this forum. Sorry if I make some mistakes when I'm writing, I'm french but I will do my best.

Here is my question :

I saw many posts and pics with a 6'' lift kit and 37'' inch tires and I want to lift mine. But do you need to change the gear ratio in the diff ??

I have a 2014, 1500 Hemi 5.7 with 3.92 gear ratio right now.

Thanks for your answers !

392's are a good gear but if you have a 2x4 456 would be a good option. The rear diff may require some grinding FYI. If you have a 4x4 leave it alone.