MPG effect of 3.92 rear end

[myram2019]

Just took a 350 mile round trip. Average speed 70. Towing trailer weighing 8500 lbs. 3.92 gears.
Final average was 8 MPG. All highway miles.

 

[Lil Miss Always Wrong]

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.

you ain't just whistling Dixie : )

every ram i had i made sure to get a 3.92, but we always got 4x4's and added lift & 35 - 37 inch tires... my 2019 ram is 4x2 and stock, and with the 3.92 i feel like i'm in my old viper srt 10 truck we had- the thing simply flies at takeoff, and passes anything on the road when i only "slightly accellerate" like a dream. I wouldn't care what the hit to the MPG was neither, i'd never go back to a 3.21.... but it has slowly been climbing, just hit 18.0 average last week... (doesn't STAY there, but it hit it : )

 

[Electrical]

Im using the website

www.fueleconomy.gov/mpg

Lets you compare to other drivers of the same truck, but going to look up fuelly, thanks.

The website is great. As for the app, I have the paid version (3 or 4 $ or something). You can enter fueling data on your phone when you're at the pump and later download into an ASCII file for Microsoft Excel.

 

[Trickster]

The website is great. As for the app, I have the paid version (3 or 4 $ or something). You can enter fueling data on your phone when you're at the pump and later download into an ASCII file for Microsoft Excel.

Then what?

 

[2wd]

Roadtrip up and down I-95. Very happy with the highway MPG performance, which included numerous traffic jams, and about 25 miles city driving mixed in.

4x4, crew cab, 3.21, non-etorque

Engine purrs along very happy in 8th gear. 87 Octane fuel to boot.

EDIT: for folks on mobile or who can't see the pic,

356 Mile Trip
Avg. 22.4 MPG
Highway speeds 70-80MPH.

 

[ExcursionDiesel]

Roadtrip up and down I-95. Very happy with the highway MPG performance, which included numerous traffic jams, and about 25 miles city driving mixed in.

4x4, crew cab, 3.21, non-etorque

Engine purrs along very happy in 8th gear. 87 Octane fuel to boot.

EDIT: for folks on mobile or who can't see the pic,

356 Mile Trip
Avg. 22.4 MPG
Highway speeds 70-80MPH.

View attachment 23603

I can't get over 18mpg at 70 unless I have a 20mph tailwind. Looks like the 3.92 is a 3-4 mpg hit for me.

 

[Electrical]

Then what?

Then nothing really

I don't always track fuel economy but when I do I might graph it to get a better look for how it's trending. This app will do graphing on the phone, but an Excel sheet on my laptop is bigger and easier to see. I also mentioned the download capability because not all fuel tracking apps allow it. If you need to archive or share your data for whatever reason, business or pleasure, an ASCII file is simple to share.

 

[SpeedyV]

I can't get over 18mpg at 70 unless I have a 20mph tailwind. Looks like the 3.92 is a 3-4 mpg hit for me.

Downhill in Entry/Exit, maybe...or tailgating an 18-wheeler

 

[Shootin' Nuke]

For me the 3:21's were the answer. "Extra get up and go" with 3:92"s???? Exactly how do you plan on getting that extra get up and go down to the pavement ? My 3:21's have trouble hooking up. Why would you pass up 2MPG for 3:92's unless you are towing heavy loads a bunch? With an 8 speed you are getting all the gear multiplication you need. If I could have purchased 2:71's I would have. Before you unload the flamethrowers, I drive almost all highway and infrequently tow lighter loads.

At the end of the day, it all comes down to individual driving style. Where you live, how many miles you drive, hauling, towing, etc.

Given your driving style you'd be silly to get anything but 3.21's.

 

[Willwork4truck]

At the end of the day, it all comes down to individual driving style. Where you live, how many miles you drive, hauling, towing, etc.

Given your driving style you'd be silly to get anything but 3.21's.

Thats literally written for me. My driving style is based on what I came out of, a 2011 Prius (so I chose the 3.21’s).
My wife had the use of a 2014 Edge Ltd.
The Prius averaged 56, the Edge 22 mpg. She gets the Ram so she’s happy, I move up from the skateboard to the Edge. Woohoo, win for everyone on comfort. Priuses are not comfortable, my longest (regular) drive was 14 hours (808 miles), that will let you know what “discomfort” is.

 

[FirstimeRAM]

With the 8 speed transmission, 1st gear has plenty of grunt with either axle ratio. I have the 3.92 and honestly should have ordered the 3.21 with my highway use. Look at all the threads on lousey mpg and you'll see that more are running the 3.92.

I got drawn into the 3.92 hype from reading these threads. Yes, the truck is quicker...but 2300 rpm on the interstate at 14-15 mpg isn't worth it for me. The truck is still slow relative to real performance vehicles. I'm not racing anyone and I don't tow over 8k.

Yeah I agree, I’m in the 3.21 crowd. If I wanna accelerate harder I’ll hop in my Camaro

 

[Willwork4truck]

Its really a hard choice due to the spread between gears. Ford had 4 choices between 3.2 and 4.1, back in 2015 (depending on trim and motor), I had picked 3.55 and most trailer towers chose 3.73. With Ram having the “2 ends of the spectrum” so to speak, its hard to balance, you either have to choose really deep or highway.
The (6 cyl) 3.55’s would have been a nice option for the hemi. I realize that the 8 spd has a good 1st and a tall 8th but still.
I had “agonized” between the 2 choices, ended up deciding on getting 3.92 for resale (I don’t tow nor do I live in mts), but then that deal fell through and voila’, I now have 3.21’s! “First world problem”...

 

[2wd]

I also wanted 3.92's originally, as I tow 3-5k frequently and 5-8k occasionally.

I came from a Ford f150 5.0 6pd with 3.55's that I was happy with the towing performance. 3.21's on the Ram seemed like a dealbreaker until I did the homework on the final drive ratio with the 3.21's and the ZF 8 spd. The Ram 3.21/8spd is actually a more tow capable setup (more mechanical advantage) than Ford's 3.55 AND Ford's 3.73 (gear for gear) with the 6 spd!

Trading the F150 for the Ram, I'm very happy to have improved my towing performance and my unloaded efficiency at the same time. Given that I'm unloaded probably 75% of the time (and frequently on the highway), I appreciate the lower RPM's and higher MPG's when cruising.

 

[SilverSurfer15]

Good thread for those who didn’t know much about this...

 

[Dusty1948]

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!

Maybe this will help you.

I've owned two Ram 1500s with a 3.92 rear axle ratio and now own a 2019 with the 3.21. All three trucks were the same body configuration: Quad Cab, two-wheel drive, Hemi. The 2010 had the 545RFE transmission which shouldn't be used for comparison. The 2014 had the 3.92 axle, 8HP70 transmission but with 20 inch wheels. My current Ram 1500 QC has 18 inch wheels.

I have maintained complete fuel consumption records for each vehicle. The lifetime average fuel economy was 17.67 for the 2010; 18.64 for the 2014; and currently 19.86 for the 2019.

My driving scenarios are mostly around town and rural roads and about 10% expressway. I cannot give you a hard figure for this since my driving scenario is never the same day-to-day. But my observation is that the 3.21 axle suffers the gas mileage more around town then the 2014 with a 3.92. Conversely, my rural and highway mileage is noticeably better with the '19 and 3.21 axle. This makes sense since start/stop driving consumes the most fuel, and with the 3.92 less throttle pressure is required for launches.

Best regards,
Dusty

2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33 gallon fuel tank, factory dual exhaust, 18” wheels. Now at: 013297 miles.

 

[JohnUSA]

you ain't just whistling Dixie : )

every ram i had i made sure to get a 3.92, but we always got 4x4's and added lift & 35 - 37 inch tires... my 2019 ram is 4x2 and stock, and with the 3.92 i feel like i'm in my old viper srt 10 truck we had- the thing simply flies at takeoff, and passes anything on the road when i only "slightly accellerate" like a dream. I wouldn't care what the hit to the MPG was neither, i'd never go back to a 3.21.... but it has slowly been climbing, just hit 18.0 average last week... (doesn't STAY there, but it hit it : )

I was on a road where two lanes merged into one. I was about 5 cars back, and signaled to move over, and the jacknut moved up and blocked me out. I tried to drop in behind him, and the other guy closed the gap to not let me in. Hmmm...time for math: Depress pedal x2"=front of pack...bwa-ha-ha-ha

 

[ExcursionDiesel]

This thread has actually caused me to think about what is possibly my only complaint with this truck. I actually feel my truck with 3:21's/8 speed has too much gear for a smooth take off from a stop. I don't like the way I have to VERY gently press the accelerator in order to get a smooth take off from a light. anything other than a gentle feathering of the pedal results in the front seat occupants being thrown into the back seat. An exaggeration of course, but it sometimes is pretty uncomfortable. Too herky jerky for me. Maybe the first twenty percent of the pedal should only equal five percent of the movement at the throttle body. Is the accelerator a fly by wire deal? If so, I suggest a reprogramming.

DO NOT get a Pulsar Tuner or Pedal Commander (both adjust the throttle response curve). If you do, your occupants will be thrown through the back window into the bed!

Actually, either of those devices can detune the throttle also. Most of us use it to make the throttle MORE sensitive though. You'd hate my truck. The pedal feels more like a switch to the average driver. I have no issues driving smoothly.

 

[Willwork4truck]

I also wanted 3.92's originally, as I tow 3-5k frequently and 5-8k occasionally.

I came from a Ford f150 5.0 6pd with 3.55's that I was happy with the towing performance. 3.21's on the Ram seemed like a dealbreaker until I did the homework on the final drive ratio with the 3.21's and the ZF 8 spd. The Ram 3.21/8spd is actually a more tow capable setup (more mechanical advantage) than Ford's 3.55 AND Ford's 3.73 (gear for gear) with the 6 spd!

Trading the F150 for the Ram, I'm very happy to have improved my towing performance and my unloaded efficiency at the same time. Given that I'm unloaded probably 75% of the time (and frequently on the highway), I appreciate the lower RPM's and higher MPG's when cruising.

Ahh, another “didnt go back to Ford” member. I would have except every configuration from Lariat up was 4-5K higher priced than a commensurate Ram, and other than the engines, nothing was as good or better with the Ford. I heard/read lots of complaints on one of the F150 forums about how “jumpy” the unloaded truck was due to rear suspension and the drop in weight due to the aluminum bed. It was true, on small bumps or washboard type surfaces the back end would dance or bounce around. I put on a full Lear canopy with a couple hundred pounds in it to calm the back down, negating their weight savings.

I too had read of the better ratios in our 8 speed, which helped me get over the hump of considering a Ram, this coming from a person whose 1st truck was a 1972 F100 in 1974, and having owned 3 more since. I’d still like to see a 3.5 range gear set in the Ram, just to give more choices.

The poster below your writeup who had driven/owned 3 rams (QC 4x2) had a good point on the around town mileage, it doesn’t vary from the 3.21 much (at least not negatively).

My last thought is how the ride of the Ram wins you over. I thought the F150 rode well but theres a noticeable improvement with the 19’ Limited. I had 18’s on the F150 S Cab and this CC has 22’s so its not like the better (softer sidewalls) tires are on the Ram. I haven’t checked wheelbases but the 2 seem close.

 

[Gen3CoupeTX]

I already commented on this thread ... But feel compelled to again. The 3.92 was a mandatory option for me. I've never once owned a vehicle and wished it had higher (lower numerically) gears. Okay, maybe back in the day when transmissions were 3 or 4 speed, and you needed to take your 4.11 or 4.56 hot rod on the interstate. I contend that with mixed use, the 3.92 isn't going to sacrifice MPG to the 3.21 ... And it would never be significant enough to make me question my choice. The little Eco light is on more than it's off. I don't use my truck for racing, as a supercharged Viper checks that block. Not street racing of course - Much too old to get busted for that!

 

[Dusty1948]

I already commented on this thread ... But feel compelled to again. The 3.92 was a mandatory option for me. I've never once owned a vehicle and wished it had higher (lower numerically) gears. Okay, maybe back in the day when transmissions were 3 or 4 speed, and you needed to take your 4.11 or 4.56 hot rod on the interstate. I contend that with mixed use, the 3.92 isn't going to sacrifice MPG to the 3.21 ... And it would never be significant enough to make me question my choice. The little Eco light is on more than it's off. I don't use my truck for racing, as a supercharged Viper checks that block. Not street racing of course - Much too old to get busted for that!

I will agree that with my 3.92 gear Rams the ECO lamp was on a lot more than my '19 with the 3.21. Since my towing requirements are now down to a few thousand pounds, I don't need the 3.92 anymore.

Best regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33 gallon fuel tank, factory dual exhaust, 18” wheels. Now at: 013355 miles.