Difference in gas mileage between the 3.21 and 3.92?

[Adrianp89]

The 3.92 will have more wear and tear, worse gas mileage, and more noise and vibration in the cab at highway speeds.

Oliver392 hit the nail on the head. My buddy has the same truck with 3.92, I have 3.21. off the line there is barely a difference. The 8sp trans makes the gear ratio much less of a factor since there is always a good gear to go to.
My biggest reason for getting the 3.21 was longevity. No matter what anyone says, 500 revolutions per minute more adds up to alot more spinning of parts over the truck's lifetime. I see no reason to have your engine turning 2k instead of 1500 while driving down the highway. I only tow a medium sized boat and only do it occasionally, but I've never had an issue with power with the 3.21's.

Unless you are towing a significant amount of weight a significant amount of the time, there is no reason to get the 3.92 unless you are planning on drag racing everyone.
..

Coming from the 3.21... the 3.92 "feels" a lot quicker and more fun to drive across the band. That alone is enough reason to get the 3.92, and is why I got a truck with it.

 

[SpeedyV]

Coming from the 3.21... the 3.92 "feels" a lot quicker and more fun to drive across the band. That alone is enough reason to get the 3.92, and is why I got a truck with it.

I could not agree more. Did I need it? Of course not. Did I want it? Of course I did.

 

[ldoh]

I recently returned from a cross country drive with some sizable mountain climbs and descends. I tended to drive a few over the listed speed limits of between 65 to 80mph and saw 17.5mpg to 18.8 mpg. I'm happy with that.

I'd much rather have the 3.92's added tow capability than the 3.21's marginal mpg improvement. The recent TFL truck utube video comparison between a 2019 Hemi Rebel 3.92 and the 2020 ED with 3.55 makes a strong argument to steer clear of 3.21 if you plan to tow/haul.

 

[jloops]

I recently took a road trip in Florida and was pleasantly surprised to get 21.9 MPG on the highway with cruise control set at 75. It is Florida so it was all flat roads, but still happy with the results.

 

[TWRam]

I recently took a road trip in Florida and was pleasantly surprised to get 21.9 MPG on the highway with cruise control set at 75. It is Florida so it was all flat roads, but still happy with the results.

I hope you were in the right lane!

J/K. Those are impressive numbers. I only get about 18-19 or so at those same speeds, more if running with a pack of cars.

 

[jloops]

I hope you were in the right lane!

J/K. Those are impressive numbers. I only get about 18-19 or so at those same speeds, more if running with a pack of cars.

Speed limits were 65-70 MPH on the road I was on. I’ve found once you start going too much over 75 the gas mileage starts to drop drastically and doesn’t really save you much time. So I’ve decided 75 is the point of diminishing returns for me.

 

[2wd]

The recent TFL truck utube video comparison between a 2019 Hemi Rebel 3.92 and the 2020 ED with 3.55 makes a strong argument to steer clear of 3.21 if you plan to tow/haul.

Respectfully disagree!

I did a lot of homework on this as I occasionally tow 7-8k lbs.

See post 165 in this thread:

3.21. vs 3.92 gear

So i found someone who can do it but the problem is the front diff has welds which makes if very difficult to change the gear and pinion. The cheapest option is to replace the hole front end housing with the 3.92 but that from the factory only currently and cost 1400. So in total its 2500-3000...

5thgenrams.com

Spoiler: Ram Hemi 3.21 w/8spd offers the same pulling power at the wheels [arguably more] than the 2016 F150 5.0 w/3.73 and 6 spd. Those Fords tow great and in my other post I linked to a TFL test of a 2016 5.0 w/3.55's doing an excellent job towing 9k lbs.

I'm not saying the 3.92 won't tow better - just debunking the claims that you can't tow with the 3.21

 

[Billy James]

Some of us older people on this forum remember the days when you would see someone pulling a 25' Fiberglass boat or a Travel Trailer with the family sedan. Those old 150 HP cars with 2.73 gears would pull heavy stuff; but it wasn't necessarily easy or safe. A 3.21 RAM will certainly pull a fairly heavy load without a problem. I have 3.92; but really that was a decision based upon my intentions to install larger tires in the future; not for towing capacity. Both 3.21 and 3.92 will work; but 3.21 will be at a greater disadvantage once you put proper truck tires on. Insofar as gas mileage; I don't think there is much difference between equally equipped 3.21 and 3.92 trucks. If gas mileage is a concern; then it looks like a 2WD, E-Torque, 3.21 RAM might be for you.

 

[Firebird]

My buddy and I have the same model Bighorn’s, he has 3.21 and I have 3.92 years. I get better in town economy, he does better hwy.

 

[Jim L]

I just picked up my 2020 ram Laramie after ordering it. Always been a 3.73 fan as a Chevy owner but ordering my first ram I went back and forth on the right gear for me. Since I primarily use my truck to pull my bassboat I went with the 3.92 and no regrets

 

[Willwork4truck]

Some of us older people on this forum remember the days when you would see someone pulling a 25' Fiberglass boat or a Travel Trailer with the family sedan. Those old 150 HP cars with 2.73 gears would pull heavy stuff; but it wasn't necessarily easy or safe. A 3.21 RAM will certainly pull a fairly heavy load without a problem. I have 3.92; but really that was a decision based upon my intentions to install larger tires in the future; not for towing capacity. Both 3.21 and 3.92 will work; but 3.21 will be at a greater disadvantage once you put proper truck tires on. Insofar as gas mileage; I don't think there is much difference between equally equipped 3.21 and 3.92 trucks. If gas mileage is a concern; then it looks like a 2WD, E-Torque, 3.21 RAM might be for you.

What? Another old fart on the forum? You mean my 1966 Pontiac Catalina wasn’t supposed to pull a 2 horse trailer with 2 horses in it?

The “Cat” wasnt powered by 150 hp motor though, a reference reminds me that: “Catalina models received the standard engine, the 389 two-barrel that was rated at 256 horsepower with base three-speed manual transmission and 8.6 to 1 compression or 290 horses with Turbo Hydramatic transmission and higher 10.5 to 1 compression. Also available as a no-cost option with Turbo Hydramatic was an economy regular-fuel 265 hp version of the 389 two-barrel with 8.6 to 1 compression ratio that burned regular gas. Other optional engines this year was a four-barrel 389 that was rated at 325 horsepower with Turbo Hydramatic or 333 with stick shift, a Tri-Power 389 rated at 338 horses, a four-barrel 421 that was rated at the same 338 hp, 353 horses with Tri-Power or the 421 HO with Tri-Power and 376 horsepower.’

Ours was the 290 hp version, ahh for the days of 29 to 32 cent a gallon gas of 91 octane...

 

[Dr. Jim]

So, at what age do you consider someone to be an "old fart?" Just want to know if I fall into that category.

 

[Trouble1233]

Speaking of gears I noticed some of you got 392 gears because you was planning on going to bigger tires..how do you recalibrate the Speed odometer nowadays??


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[Willwork4truck]

So, at what age do you consider someone to be an "old fart?" Just want to know if I fall into that category.

I'd say if you had a drivers license when gas was under 50 cents a gallon...
I looked it up as my memory is, well, not as sharp as a tack anymore (maybe a wadded up tissue):
"The average price of a gallon of gasoline in May 1973 was 38.5 cents a gallon. By June 1974, it had risen to 55 cents a gallon."

I was licensed in, you guessed it, May 1973...

 

[Billy James]

What? Another old fart on the forum? You mean my 1966 Pontiac Catalina wasn’t supposed to pull a 2 horse trailer with 2 horses in it?

The “Cat” wasnt powered by 150 hp motor though, a reference reminds me that: “Catalina models received the standard engine, the 389 two-barrel that was rated at 256 horsepower with base three-speed manual transmission and 8.6 to 1 compression or 290 horses with Turbo Hydramatic transmission and higher 10.5 to 1 compression. Also available as a no-cost option with Turbo Hydramatic was an economy regular-fuel 265 hp version of the 389 two-barrel with 8.6 to 1 compression ratio that burned regular gas. Other optional engines this year was a four-barrel 389 that was rated at 325 horsepower with Turbo Hydramatic or 333 with stick shift, a Tri-Power 389 rated at 338 horses, a four-barrel 421 that was rated at the same 338 hp, 353 horses with Tri-Power or the 421 HO with Tri-Power and 376 horsepower.’

Ours was the 290 hp version, ahh for the days of 29 to 32 cent a gallon gas of 91 octane...

Well, the 1966 Catalina was certainly one of my favorites; especially the 2+2. The 421 in those things was no joke; but still by today's standards isn't a lot of HP for a high performance car. When I mentioned the 150 horse power cars, I was more referencing the 70's and 80's cars that were neutered by "smog" controls. I had a neighbor who towed his 25 foot boat with a 1976 Chrysler Cordoba (170 hp / 280 lb/ft torque); that thing struggled the whole way and the back bumper was nearly dragging on the ground. Watching him pull that boat out of the water was amusing; it was like a burnout contest and a tractor pull all in one. I also recall traveling the PA turnpike as a kid and passing all these sedans red lining just to make about 30 MPH getting up the hills in western PA while pulling those old heavy travel trailers. Vehicles have come a very long way insofar as capabilities and efficiency for sure. And yes, I do miss the days of cheap gas. I don't recall 29 to 32 cent gas, but I do remember 60 cent gas; I could cruise all weekend for $5 worth of gas.

 

[Adrianp89]

Well, the 1966 Catalina was certainly one of my favorites; especially the 2+2. The 421 in those things was no joke; but still by today's standards isn't a lot of HP for a high performance car. When I mentioned the 150 horse power cars, I was more referencing the 70's and 80's cars that were neutered by "smog" controls. I had a neighbor who towed his 25 foot boat with a 1976 Chrysler Cordoba (170 hp / 280 lb/ft torque); that thing struggled the whole way and the back bumper was nearly dragging on the ground. Watching him pull that boat out of the water was amusing; it was like a burnout contest and a tractor pull all in one. I also recall traveling the PA turnpike as a kid and passing all these sedans red lining just to make about 30 MPH getting up the hills in western PA while pulling those old heavy travel trailers. Vehicles have come a very long way insofar as capabilities and efficiency for sure. And yes, I do miss the days of cheap gas. I don't recall 29 to 32 cent gas, but I do remember 60 cent gas; I could cruise all weekend for $5 worth of gas.

Figuring 55 cent gas in 1974 is equivalent to $2.86 today - and I can get gas in the $2.20s right now - the price of gas is quite a bit cheaper today, or would be around 43 cents in 1974.

 

[Dr. Jim]

I was licensed in, you guessed it, May 1973...

Oh, jeez, I already had my driver's license for several years when that 1966 Catalina was new.

 

[SacRebel]

All I can say is my Rebel with eTorque and the tow package (3.92) is averaging 12 mpg after 6,000 miles..albeit about 90% city driving. FCA has been absolutely no help in resolving the far below EPA stated numbers of 17/19/22. Hoping someone will eventually file a class-action lawsuit against them for misrepresenting the mileage numbers.

 

[Firebird]

All I can say is my Rebel with eTorque and the tow package (3.92) is averaging 12 mpg after 6,000 miles..albeit about 90% city driving. FCA has been absolutely no help in resolving the far below EPA stated numbers of 17/19/22. Hoping someone will eventually file a class-action lawsuit against them for misrepresenting the mileage numbers.

I started getting better economy at around 9,000 miles, maybe your will improve soon

 

[pber1]

Majority of trucks come with the 3.92 gear ratio.
The ones with 3.21 aren't the ones I prefer due to color, model, options, etc....
No plans to haul/tow so trying to stick with the 3.21, but curious to know the gas mileage difference people are seeing between the 3.21 and 3.92 for daily use driving in case I have to opt for the 3.92.

With 3.21’s I was getting 23hwy at 70mph stock.