3.21. vs 3.92 gear

[silver billet]

I'm pretty sure 5000 pounds is a general rule/target for all half tons, and usually 2500-3000 for smaller trucks and SUVs.

In any case, there are youtube videos showing the effect (with real calculations, not vague hand waving and "I think it looks...") of airbags vs WDH, and it's no contest, really; WDH does a much better job at leveling than any airbag system does. Not only does it level the truck better, it makes the truck pull/tow better, it's a win all around (except that it's more complicated and messy to setup, especially if you don't own the truck/trailer in question)

 

[twonine]

I’m looking to place an order and I’m not sure of which gear ratio to order. 95% of the time I will be driving the truck empty. Gas mileage is important to me so I’m ordering the e-torque engine. I tow a small trailer that weighs 4000 lbs and only do it 6-8 weekends a year.

My concern is that the 3.92 gear is going to kill the gas mileage. The 3.21 just seems a bit low for a truck of this size.

Looking for the mpg difference between the two in every day driving.

Thanks

Good morning
I purchased a new Ram 1500 Bighorn 5.7 w/o e-torque a couple of months ago and had the exact same concerns. My commute to work and back every day is about 90 miles, all freeway driving. I elected to go with the 3.92 rear end after finding out that the difference in fuel mileage between the two ratios if very small. I have a 6,000 travel trailer that I take camping and the towing benefits outweigh the minor difference in MPG all day long. The truck is 3 months old and I have 6,500 miles on it already. I have a very heavy foot (I rarely drive under 80 to and from work) and I'm averaging around 17.5 MPG for the entire tank. I'll get low 20's on the freeway, and around 14-15 while in town. Hope that info helps your decision.
Have a great afternoon!

 

[Willwork4truck]

I’ve already stated my preferences for a gear ratio (I wanted a 3.92 but settled for a 3.21) however the mpg’s for the 3.21 when not even broken in on a 200 mile trip, averaging 60-65 with some small town stoplights was an impressive, 23.6. The photo shows 23.4 but I got better.

 

[mangus2k20rebel]

I’m looking to place an order and I’m not sure of which gear ratio to order. 95% of the time I will be driving the truck empty. Gas mileage is important to me so I’m ordering the e-torque engine. I tow a small trailer that weighs 4000 lbs and only do it 6-8 weekends a year.

My concern is that the 3.92 gear is going to kill the gas mileage. The 3.21 just seems a bit low for a truck of this size.

Looking for the mpg difference between the two in every day driving.

Thanks

I would do 3.92, the 3.21 gcwr is very low and it won’t help your tranny

 

[riccnick]

I have the 3.21 and have towed pretty heavy with it. Truck handles it just fine, there is no need for more power towing through the very hilly area I used to live in.



However, I will say, I don't see the mpg benefit of the 3.21's, (or eTorque), as I get a mixed average of around 14-15 and on the highway I get less than 20 at best. (I'm rated 17/22/19 with eTorque) Towing is towing, and 10mpg or less is expected when towing heavy or something with a large cross sectional front area.

My point is though, you won't miss the power if you go 3.21 and don't need to tow more than 8k, however, you won't miss the mpg "advantage" if you go 3.92's either.

 

[cotonymopar]

3:92 gears on my 03, 12, and now my 19... would not go without.. I sometimes have loads in the back, or pulling a trailer, I love the 3:92s... live in Colorado with many hills and mountains.

 

[2wd]

I originally wanted a 3.92 as well until I did the homework on the transmission (the effect of the 8 gears vs. 6 speeds that were most common just a few years ago). You can checkout post 165 for details.

The upshot however is that the Ram 3.21 w/8 speed provides equal or better final drive ratio than 2016 F-150 3.73 6 speed gear for gear. [3.73 was the best towing gear for the F150 2011-2016]. Folks talking down the 3.21's capability (in this truck) might as well suggest that pre 2017 3.73 F150's be traded in if they are serious about towing!

Seriously though, if hooked up to a trailer frequently, tons of mountain driving, putting on huge tires, 3.92 is the way to go. But to say you can't tow with the 3.21 is simply not the case anymore thanks to the ZF 8 Speed.

And for what it's worth, I recently got 24.3 MPG average on a 750 mile trip.

 

[Willwork4truck]

I like a challenge, I’ll beat your 24.3 even if it means coasting down the mts...
There may be 1 mile of peed off drivers behind me as I draft the semi in front of me going 45 but I’ll see 24.4!

Seriously, coming from old school low hp/tq engines and 3-4 spd transmissions of the 70’s and 80’s, where a 4.10 was about mandatory to tow with, I can easily justify either ratio (as long as you aren’t towing more than recommended by RAM). It’s the “fun factor” that’s hard to quantify, some will never give up 3.92’s for that reason alone.

 

[2wd]

I like a challenge, I’ll beat your 24.3 even if it means coasting down the mts...
There may be 1 mile of peed off drivers behind me as I draft the semi in front of me going 45 but I’ll see 24.4!

Seriously, coming from old school low hp/tq engines and 3-4 spd transmissions of the 70’s and 80’s, where a 4.10 was about mandatory to tow with, I can easily justify either ratio (as long as you aren’t towing more than recommended by RAM). It’s the “fun factor” that’s hard to quantify, some will never give up 3.92’s for that reason alone.

Right on sir! I'm not in my 20's - this truck is not my fun vehicle - it's a means to an end. I have other toys this thing pulls if I want the thrills. However it's a good point that for some folks this is their fun vehicle and they want to do burnouts and tunes and mods and such, and 3.92 is preferred for that reason alone.

Long interstate hauls with family and light loads are my primary use. Frequent towing 5K or less, and occasionally towing up to 8-9k lbs. I want the lowest operating costs (fuel) and lower engine wear and tear (purring along at 1450 RPM) over 150,000 plus miles of hopefully trouble free use.

 

[silver billet]

You can't have it both ways; either the difference between the 3.21 is significant enough to notice (in which case MPG will be significantly reduced with the 3.92 and towing ability significantly increased) or it is marginal in which case you won't notice much different in towing or MPG.

I have the 3.21, and from what I understand, the 3.21 in 7th gear is pretty much equal to engine rpms of 3.92 in 8th gear. So in that case, there is a pretty noticeable difference in MPG, at least in my truck between those 2 gears. And if I'm towing a load I can always just restrict to 7th or 6th as needed for towing at interstate speeds.

So I'm not sure what the 3.92 gives you, other than more grunt from a stop, off the line. Once you're moving and gears are shifting, the 2 gear ratios should be functionally equivalent in terms of towing and MPG (but possibly using different gears at the same speed) until they reach 8th gear at which point the 3.92 will be revving higher for the same speed.

 

[NDanecker]

So I'm not sure what the 3.92 gives you, other than more grunt from a stop, off the line. Once you're moving and gears are shifting, the 2 gear ratios should be functionally equivalent in terms of towing and MPG (but possibly using different gears at the same speed) until they reach 8th gear at which point the 3.92 will be revving higher for the same speed.

You will have more gears to play with when you are not driving at highway speeds. For example, do you remember the days of the 3 and 4 speed trucks? You'd have to really spin up the motor before it will shift to 4 and most times it will be to early so you'll have to down shift again to 3rd. Many times when towing you'll be too high for 3 but too low for 4 so the truck hunts back and forth. Having more gears will help keep the motor in a smaller RPM range which saves fuel and increases driveability. I"ll take a hit in MPG having 8 speeds vs. 6 speeds when towing.

 

[silver billet]

You will have more gears to play with when you are not driving at highway speeds. For example, do you remember the days of the 3 and 4 speed trucks? You'd have to really spin up the motor before it will shift to 4 and most times it will be to early so you'll have to down shift again to 3rd. Many times when towing you'll be too high for 3 but too low for 4 so the truck hunts back and forth. Having more gears will help keep the motor in a smaller RPM range which saves fuel and increases driveability. I"ll take a hit in MPG having 8 speeds vs. 6 speeds when towing.

I wrote a reply and then deleted it; got confused by your response.

Please explain how you get more gears to play with with the 3.92? These are both 8 speeds, and once both trucks are between 2 and 7, there is no difference. Yes at 30/40/50 mph the two trucks might be in a different gear while traveling at that speed, but that doesn't mean anything. The only difference is in the extremes; taking off from a stop (first gear) and traveling at interstate speeds (in 8th gear). While not at those 2 extremes, both trucks have the ability to shift up/down as needed, and they probably both use the same RPM cutoffs/thresholds while doing so.

(Not arguing, just wondering if I'm wrong and missing something )

 

[Davidmurphy02]

I've towed a small fifth wheel - 5,000 pounds loaded - over many mountain ranges between British Columbia and Texas. The 3.21 had plenty of power, I was able to accelerate going uphill when I needed to at any altitude and on any grade. In tow mode the transmission doesn't use 8th but cruises easily in 7th, downshifts as needed when climbing very smoothly. When not towing I've seen 24 mpg in highway driving. Towing mileage varied a good bit depending on terrain and conditions, between 12.5 and 15.

This is a completely different experience than my 1998 Ram 5.9, 4 speed OD with 3.55, towing a similar size and weight trailer. Never had enough power, struggled mightily when climbing and always had the feel of hauling a huge load. With the 2019 I am able to drive just about like I would without the trailer, performance is outstanding. I am satisfied with the 3.21, and like the highway mileage I get with it when not towing. The 8 speed and the Hemi power are an unbeatable combination.

 

[SpeedyV]

I originally wanted a 3.92 as well until I did the homework on the transmission (the effect of the 8 gears vs. 6 speeds that were most common just a few years ago). You can checkout post 165 for details.

The upshot however is that the Ram 3.21 w/8 speed provides equal or better final drive ratio than 2016 F-150 3.73 6 speed gear for gear. [3.73 was the best towing gear for the F150 2011-2016]. Folks talking down the 3.21's capability (in this truck) might as well suggest that pre 2017 3.73 F150's be traded in if they are serious about towing!

Seriously though, if hooked up to a trailer frequently, tons of mountain driving, putting on huge tires, 3.92 is the way to go. But to say you can't tow with the 3.21 is simply not the case anymore thanks to the ZF 8 Speed.

And for what it's worth, I recently got 24.3 MPG average on a 750 mile trip. View attachment 28208

Haha...I’d be the guy to opt for the 4.30 rear end in the F-250 gasser

 

[NDanecker]

This is a completely different experience than my 1998 Ram 5.9, 4 speed OD with 3.55, towing a similar size and weight trailer. Never had enough power, struggled mightily when climbing and always had the feel of hauling a huge load. With the 2019 I am able to drive just about like I would without the trailer, performance is outstanding. I am satisfied with the 3.21, and like the highway mileage I get with it when not towing. The 8 speed and the Hemi power are an unbeatable combination.

You compare to a lesser vehicle and feel the 2019 with 3.21 are more than adequate and 'unbeatable'. I come from a world of 3500 diesels with 4.10 and AISIN's transmissions so my experiences are the opposite. Case in point - all experiences vary and opinions are relative to which is best. Buy what makes you feel happy! I would never be happy with a 3.21 gear set especially after towing a simple 7 x 14 empty cargo trailer.



Safe towing guys.

 

[Jus Cruisin]

You compare to a lesser vehicle and feel the 2019 with 3.21 are more than adequate and 'unbeatable'. I come from a world of 3500 diesels with 4.10 and AISIN's transmissions so my experiences are the opposite. Case in point - all experiences vary and opinions are relative to which is best. Buy what makes you feel happy! I would never be happy with a 3.21 gear set especially after towing a simple 7 x 14 empty cargo trailer.



Safe towing guys.

That's a, for sure, apples to oranges comparison. I had a dually Cummins a few trucks back. What does that have to do with gasser gearing? I don't care what gear is in these trucks they are all slugs compared to little 4 banger rice rockets or a Challenger or a new F150 Limited with the Raptor engine. If 3.92's make you feel like your driving a pro mod , good for you. That's all that matters. I don't have to mat my truck to stay with traffic with or without the enclosed car trailer with my Camaro in it. This truck is my "Lincoln Town Car " that just happens to be able to carry wood, stones, appliances along with people comfortably. That's what makes me happy.

 

[NDanecker]

That's a, for sure, apples to oranges comparison. I had a dually Cummins a few trucks back. What does that have to do with gasser gearing? I don't care what gear is in these trucks they are all slugs compared to little 4 banger rice rockets or a Challenger or a new F150 Limited with the Raptor engine. If 3.92's make you feel like your driving a pro mod , good for you. That's all that matters. I don't have to mat my truck to stay with traffic with or without the enclosed car trailer with my Camaro in it. This truck is my "Lincoln Town Car " that just happens to be able to carry wood, stones, appliances along with people comfortably. That's what makes me happy.

I sold the Trackhawk because I couldn't do what I was used to do (tow, carry, etc) in the dually. That car was AWESOME, fast and fun to drive. I miss it, but can't have 2 cars nor do I want to deal with 2 cars. When the Ram Hellcat comes out I'll be sure to be first in line. Why? Because that would make ME HAPPY and fit my current lifestyle. To each there own....

 

[DraKhen99]

The towing chart shows a significant allowable load difference between 3.21 and 3.92-equipped trucks. 8,150 versus 11,250, to be exact (via RAMTrucks.com). There's gotta be a reason the manufacturer lists those towing numbers, given the cab/engine/bed/drive type are all the same.

I bought the 3.92s because I want the get-up-and-go, and on road trips I have the truck loaded and go up and down the mountains. I'm willing to pay an MPG penalty for that capability.

-John

 

[silver billet]

Can someone please explain to me how mountains somehow change which gear ratio works better? I'm genuinely curious, because my understanding of this is obviously incorrect then. To me, as long as you are driving a speed which the transmission would use 2 - 7 for, there should be no difference between the two trucks. If you're going up a mountain in gear 6 and it's starting to lug with the 3.21, then it just downshifts to 5 instead. I fail to understand why having a 3.92 somehow changes that whole concept.

 

[DraKhen99]

Can someone please explain to me how mountains somehow change which gear ratio works better? I'm genuinely curious, because my understanding of this is obviously incorrect then. To me, as long as you are driving a speed which the transmission would use 2 - 7 for, there should be no difference between the two trucks. If you're going up a mountain in gear 6 and it's starting to lug with the 3.21, then it just downshifts to 5 instead. I fail to understand why having a 3.92 somehow changes that whole concept.

It's all about torque multiplication. The lower (numerically higher) gear ratio multiplies the torque. Using round numbers, if your truck is producing 100lbft of torque and you have the 3.92 RAR, ignoring the rest of the drivetrain, your truck is putting 392lbft of torque to the ground. A 3.21-equipped truck would have 321lbft of torque going to the ground in the same scenario. That's about a 20% difference, hence in our simplified example, the truck with 3.21s will be working about 20% harder to go up that hill.

That's how I understand it, someone please correct me if I'm wrong.

-John