MPG effect of 3.92 rear end

[rott]

I haven't found a concrete answer...or really any semi-firm answer even on this. I've read the 3.21 is a little "ho-hum" off the line, but the 3.92 would be significantly better. Does that rear end cause a noticeable drop in MPG, either city or highway?

 

[devildodge]

Unless you are going for absolute maximum mileage and you are going to drive ultra conservative, the 3.92 benefits will far outweigh the 3.21 gas savings

 

[SpeedyV]

Unless you are going for absolute maximum mileage and you are going to drive ultra conservative, the 3.92 benefits will far outweigh the 3.21 gas savings

That, my friend, is the God's honest truth when it comes to pickup trucks.

 

[rott]

Thank you both for your input, and I'm sure I'll be following your recommendation! If there really isn't a difference in MPG, then why is FCA offering the 3.21 at all? The logical side of me says that they had to have a reason to offer the 3.21...but what is that reason?

I'm so glad I found this forum, as I've learned a lot...I'm very thankful I didn't already order one, as this forum has modified some of the choices I would have made 2 months ago!

 

[ryelinek]

I live in Northern VA and commute about 30 miles into work 3 days a week in a fair amount of stop and go. My truck has a 3.92 Axle and for the first 1300 miles I’m averaging around 17.5 which I am quite pleased with.

 

[devildodge]

The 3.21 does serve a purpose. If you would buy a 4x2 and drive mostly all highway, unloaded...you would notice the extra Mpg. But if you use your truck, are pushing around that transfer case and front axle and drive with a heavy use of your right foot, it won't help much and in some cases will be a hindrance.

But the HFE is coming, can't wait to see what it can do...but I have a 488 cu in V10, I don't convern myself with gas mileage, just a good idea of where the gas stations are.

 

[FLG8R]

I haven't found a concrete answer...or really any semi-firm answer even on this. I've read the 3.21 is a little "ho-hum" off the line, but the 3.92 would be significantly better. Does that rear end cause a noticeable drop in MPG, either city or highway?

Had a 2015 Ram Crew Cab with the 3.21 and had no trouble getting 20mpg. That said, I now drive a lighter Reg Cab with the 3.92 and get around 18mpg. There could be a 10mpg difference between the two and I'd never give up my 3.92. The get up and go is tremendous with this ratio compared to the 3.21.

 

[Jared B]

I can knock down 22-23MPG highway with my 2016 Crew 4x4 with the 3.92s. I personally think the fuel economy difference between the 3.21s and 3.92s would be negligible.

 

[rp781]

Wish I would have read this before I ordered the 3.21. Do mostly highway driving, not towing and went that route for the MPG.....sounds like it's a wash either way only better acceleration on the 3.92....oh well

 

[alwi228]

Wish I would have read this before I ordered the 3.21. Do mostly highway driving, not towing and went that route for the MPG.....sounds like it's a wash either way only better acceleration on the 3.92....oh well

No kidding! I feel like a chump over here in my 3.21's lol

 

[Jared B]

Nothing wrong with the 3.21s, the ratio spread of the 8 speed makes it act as if it was a higher gear ratio in a 6 speed truck anyways. The 3.92s do give you a bit more get up and go off the line but I wouldn't say its significant.

 

[rott]

I thought this question was going to get me laughed at...now I'm definitely glad I asked it! lol

 

[devildodge]

It seems from all the conversations we have had about this, that 3.73 is absolute best of all gears.

Obviously the 1500 doesn't offer that.

3.55 is a great ratio...only on the V6

3.92 is a good towing gear and probably similar to the old go to 4.10 with near the power and better mpg.

And the more people I can convince to get 3.92 is more availability on the used market

 

[devildodge]

I thought this question was going to get me laughed at...now I'm definitely glad I asked it! lol

We talk about it quite often. It is an interesting thing.

@Jared B has there been any info on the HFE. And as many people are surprised about the lack of info on Hemi ETorque, what about the V6...want to hear about the 3.55 and the V6...

 

[Jared B]

We talk about it quite often. It is an interesting thing.

@Jared B has there been any info on the HFE. And as many people are surprised about the lack of info on Hemi ETorque, what about the V6...want to hear about the 3.55 and the V6...

HFE Article I did write an article about the upcoming HFE back in April. Haven't heard anything new about it since.

 

[RAM 4times]

Wish I would have read this before I ordered the 3.21. Do mostly highway driving, not towing and went that route for the MPG.....sounds like it's a wash either way only better acceleration on the 3.92....oh well

i agree. i would have went with the 3.92 on my 19 order but i have the 3.21 on my 13 and it is fine. now when i get another ram in a few years i would go with the 3.92 from all the info on this site.

 

[devildodge]

The "drive cycle," which is how fast and where you drive, is also an important consideration when selecting the right axle ratio, according to truckmaker Ram. For lower speeds and rural driving, a higher gear set will add capability and a more spirited driving experience without too much damage to the final mpg number, according to Ram. But if you do a lot of high-speed driving, you might want to consider a vehicle with a numerically lower gear set to decrease engine rpm and improve fuel economy.

With the 8spd transmission you really have ro decide what means more to you.

Now back in the day of 3spd transmissions you really either got mpg or towing they wouldn't do both at all.

But now you can get the higher gear ratio and have some good mileage or get the lower ratio and still be able to tow something of substance.

 

[alacombe]

I do 99.9% city driving and I have the 3.92 on my 2019 Ram. My MPG is approx 13.5mpg right now but I am only at 220 miles so the engine isn't even broken in yet.

 

[RAM 4times]

I do 99.9% city driving and I have the 3.92 on my 2019 Ram. My MPG is approx 13.5mpg right now but I am only at 220 miles so the engine isn't even broken in yet.

you seem like me and don't put a lot of miles on your truck. i do a lot of city driving too.

 

[alacombe]

you seem like me and don't put a lot of miles on your truck. i do a lot of city driving too.

I average about 8000 miles a year. When I traded in my 2016 Ram it only had about 16,000 miles on it