Rear axle ratio vs mpg.

[Yardbird]

The 3:55 is the best ratio for the V6.

You got that right. I have a 3.21. I lock out 8th when I drive it. It's useless with a high revving V-6

 

[Poncherello]

I think the 3.92 8spd would be great for 3.6, just because that engine seems to be happy in the mid range. Anyway I have the 3.92's, 8 spd with the 5.7 and from 80mph on, it's real happy lol! Moreover, if it came with 4.11's it would be happier. Anyway, I bought my Ram this way also with the plan of upsizing the tires slightly from 33's to 34's or 35's.

 

[ramffml]

My 2016, 5.7 w/ 6spd. auto has 3.55's it is only turning 1900 RPM at 65 MPH, that's just over idle? I looked for a long time to find what I bought, would not take one with the 3.21's * speeds do you no good if it never shifts into those upper gears. I would prefer a 6 Speed manual!!!! In my Dakota 4.7, 3.55's, 5 spd. manual , most of the time just used 2,4, 5 and I was in 5th by 30-35mph. Biggest cause of poor MPG is how hard you accelerate not how fast you cruse. Everyones in a rush to leave the stop light to get to the next one and sit there!!!

Just so you know, the 8 speed with 3.21 absolutely destroys the 6 speed with 3.92. Not even a contest, it has a shorter first gear for more tugging off the line, taller overdrive for better mpg and lower highway rpms, and gives you two more gears to play with.

I would not take the 6 speed over the 8 with any gear ratio, not even with standard.

 

[Wild one]

My 2016, 5.7 w/ 6spd. auto has 3.55's it is only turning 1900 RPM at 65 MPH, that's just over idle? I looked for a long time to find what I bought, would not take one with the 3.21's * speeds do you no good if it never shifts into those upper gears. I would prefer a 6 Speed manual!!!! In my Dakota 4.7, 3.55's, 5 spd. manual , most of the time just used 2,4, 5 and I was in 5th by 30-35mph. Biggest cause of poor MPG is how hard you accelerate not how fast you cruse. Everyones in a rush to leave the stop light to get to the next one and sit there!!!

You're getting your idea from 1 guy with a V6,the 5.7's shift into the higher gears under most circumstances,takes a fairly decent grade for them to start down shifting.If the majority of your driving is 75+ mph/freeway speeds the 3.21's are the ones you want,as you'll get better milege,and the big one,is your oil temps will be significantly lower.

 

[Zac1]

You can buy a lot of gas for for the cost of changing. If you plan to trailer you will be happier with 3.92.

 

[Benhudson169]

I have a 2013 ram 1500 with the 3.6 4x4, 8spd and had mine swapped from 3.21 to 3.92 and I haven’t seen more than a 1.5 mpg drop. So I can’t imagine you’d see a 1 to 2 mpg gain.

 

[Bandit1859]

2021 1500 etorque hemi 4x4 3.92 axle. If I swapped to 3.23 what Change in mpg might I expect? What is a ballpark on having that work done? Also, as 4x4 is there any corresponding change to the front drive? Appreciate any info.

I have both trucks. Only 2-300 rpm difference. Gas mileage minimal at best not worth the effort or money

 

[TestPilot57]

The 17's on the 1500's are a 31" tall tire,the 20's on the 1500's are a 33" tall tire,differance divided by 2 = 1" raised ride height

This is the 5th gen forum. 5th gens do not have 17" wheels. They can't. There isn't clearance for the brakes (without modification).

The two factory options for 5th gens are 275/65R18 (32.07" dia) or 275/55R20 (31.91" dia). Virtually identical.

 

[Wild one]

This is the 5th gen forum. 5th gens do not have 17" wheels. They can't. There isn't clearance for the brakes (without modification).

The two factory options for 5th gens are 275/65R18 (32.07" dia) or 275/55R20 (31.91" dia). Virtually identical.

You might want to go back to post 14 and 15,and re-read them . I was replying to post 14,and you seemed to have missed that fact. The majority of guys replying on this thread have 4th gens,just in case you missed that fact to.
Little tidbit for you,i know there's no 17's on the 5th gens,but that wasn't what i was replying to,i was replying to GT's post about raised ride height.

 

[huntergreen]

As a counterpoint: my truck lives in 8th gear (literally). I bet 95% of its life is 8th gear, and yes that includes many hours of "rolling terrain". I'm also on 20 inch rims (stock diameter though).

Downshifting is not some boogyman either, it's a seamless 400 rpm increase and if you have tunes on or you're talking in a conversion its completely unnoticeable. The point of having all these gears, is to use them at times likes this. The truck always has a gear that makes the most sense, who cares if it drops a gear? That's why you have 8 of them.

And don't forget, when you're in the city: the 3.92 usually creates 1 extra upshift/downshift vs the 3.21, it uses more gears to get to the same speed. So if you're THAT concerned about shifting, then be honest and mention that the 3.92 is definitely more busy in the city.

Pick your poison.

For me, nothing better than cruising on the freeway at 1400 to 1500 RPMs for hours at a time, the truck is just idling its way through life with minimal drama.

Though I absolutely agree that the time for the 3.21 is when you're buying the truck, probably too late at this point unless the truck is brand new and you plan to drive the wheels off it.

Edit: ok I just realized you have the 3.6 with the 3.21. Completely different story, I know nothing about how that drive train feels. The hemi/3.21 is glorious though, no complaints. The OP drives a hemi, not the 3.6.

What’s your normal cruising speed when in 8th gear ? Thanks