3.21 vs 3.92

[19llhpb]

To each their own on gear ratio selection, what is best for your situation. Plenty of great info and advice on this forum to make a very educated decision. I went with 3:92’s for towing and adding 35” tires. ALSO, with the 3:92’s my truck has a higher towing capacity than my wife’s Expedition, with the 3:21’s it would not have. Can’t let her rig out tow mine!

 

[DMXS]

I went with the 3.21s.....having two trucks with 3.55s I really wish Ram would offer that rear end. From my research - the 3.92 in 8th gear is the same final drive ratio as the 3.21s in 7th gear.

90% of the time it's just me in the truck....we'll see soon if I made the right choice! I'm planning on taking a slight MPG hit going to Ram from my 2.7l ecoboost....didn't want the hit of 3.92s as well (I drive 30,000 miles a year).

Well how do you like the 321 gears and what kind of MPG are you getting?

 

[RichM1983]

I have a Laramie with the 3.92 gear and only 300 miles and I’m getting right under 16mpg. Mostly highway miles.

 

[MrHankbot]

3.21 gears unless you want the extra hauling capability, never drive on the interstate, want the truck to be just a little tiny bit quicker, or just don't care what your mpg turns out to be.

For me the only 2 that really matter are towing capacity and mpg. And towing capacity won out since we own a camper and may get a little larger one some day.

The interstate in NE is 75mph, every time I drive on it I regret going the way I did, a little. However if we ever buy a larger camper I will definitely be glad for the 3.92's.

 

[Creep0321]

3.21 gears unless you want the extra hauling capability, never drive on the interstate, want the truck to be just a little tiny bit quicker, or just don't care what your mpg turns out to be.

For me the only 2 that really matter are towing capacity and mpg. And towing capacity won out since we own a camper and may get a little larger one some day.

The interstate in NE is 75mph, every time I drive on it I regret going the way I did, a little. However if we ever buy a larger camper I will definitely be glad for the 3.92's.

How big is your current camper?


Sent from my iPhone using Tapatalk

 

[Ramit392]

I found this 16 page thread to be informative and helped reassure that I won’t regret having the 3.21.

https://www.ramforum.com/threads/3-21-gear-ratio-anyone-actually-towing-with-it.43001/

You should be just fine with 3.21 gears. The 3.21 can very near pull with the 3.92 IMO. I think if your pull is around 9000 lbs or over a 3.92 would be better fit. Most folks with a 1/2 Ton truck is not pulling much over 8500 Lbs max.The new TT are much lighter in weight than the older TT were for sure. I have seen 36 Foot TT with a couple slides only weighing in about 7700 Lbs.!

 

[Lil Miss Always Wrong]

We got two 2019 Rams last week, one WITH 3.21 and one with 3.92. The one with 3.21 was used, so it has 6K miles on it and is seeing better gas milege, but the one with 3.92 barely has 300 miles on, so its not really apples to apples, engine is brandy new. Plus, the two are only highway/city but zero towing..... And the one with 3.21 hubby has already leveled and put Pro Comp 34 inch tires on, and mine is stock/stock/stock. I would say (this is my 8th RAM with the 3.92) it definitely takes a 1-2 mpg hit but whenever i test drive the 3.21 they feel alittle sluggish to me COMPARED to 3.92.

 

[ExcursionDiesel]

We got two 2019 Rams last week, one WITH 3.21 and one with 3.92. The one with 3.21 was used, so it has 6K miles on it and is seeing better gas milege, but the one with 3.92 barely has 300 miles on, so its not really apples to apples, engine is brandy new. Plus, the two are only highway/city but zero towing..... And the one with 3.21 hubby has already leveled and put Pro Comp 34 inch tires on, and mine is stock/stock/stock. I would say (this is my 8th RAM with the 3.92) it definitely takes a 1-2 mpg hit but whenever i test drive the 3.21 they feel alittle sluggish to me COMPARED to 3.92.


View attachment 12098

Lol. Seems like y'all should have swapped trucks. The 3.92 with 34's would have been a better combo!

 

[Lil Miss Always Wrong]

Lol. Seems like y'all should have swapped trucks. The 3.92 with 34's would have been a better combo!

So true BUT he's a "black and chrome guy" while i am a "stealth matte black all the way gal"...lol

 

[racr748]

If we take the "sluggish" response aspect of the 3.21 vs 3.92 out of the equation , we can look at it from a strictly math/cost per mpg perspective.

Assumptions: 23g tank. 3.21 @17mpg vs 3.92 at 15mpg
Average miles/tank: 3.21 at 391miles/tank vs 3.92 at 345miles/tank
Decreased difference of 46miles of driving/tank

 

[Gondul]

Decreased difference of 46miles of driving/tank

More Coffee Stops!

 

[SpeedyV]

If we take the "sluggish" response aspect of the 3.21 vs 3.92 out of the equation , we can look at it from a strictly math/cost per mpg perspective.

Assumptions: 23g tank. 3.21 @17mpg vs 3.92 at 15mpg
Average miles/tank: 3.21 at 391miles/tank vs 3.92 at 345miles/tank
Decreased difference of 46miles of driving/tank

If anything, you make a convincing argument for the 33-gallon tank. It’s nice going 400-500 miles between fill-ups (without running too low)!

 

[Gman]

I negotiated on the RAR, but the 33 gallon tank was a must have.

 

[dinohuby]

I guess it’s a mute point because I am getting the 3.92 either way for towing purposes but I was curious if anyone knows what mpg differences to expect with the 3.92 instead of the 3.21

I have 33 tires and 392 gears on my 2019 ram 5.7l DTS ( the non hybrid engine) and the mileage was 13 city and 15 hwy until i installed a magna flo muffler and a cold air intake. After that i went to 15 city and 17 hwy if i keep it at 70and if i go 60 i get 18 MPG but i have a friend with a rebel hybrid with 3.92 gears and he only gets 18 MPG hwy without my alterations and same tire size. He hates comming to stop lights in the summer because the motor auto shuts down and his A/C gets hot! I just wish that i could actually get the 20 MPG that i was supposed to get on the hwy!!

 

[Ramit392]

I can get 19.5 to 20.0 MPG on the open hwy. In town what little I drive in town I get about 15, That said I have the 3.92 stock with a drop in air filter and hybird. The AC will stay cool when it stops and if AC senses temp drop from settings the motor starts on it own to keep AC running and cool. Not sure why one would shut off and get hot with out air. On extreme hot days last summer some times it would not shut off at all in town.

 

[2019REBEL]

I can get 19.5 to 20.0 Mph on the open hwy. In town what little I drive in town I get about 15, That said I have the 3.92 stock with a drop in air filter and hybird. The AC will stay cool when it stops and if AC senses temp drop from settings the motor starts on it own to keep AC running and cool. Not sure why one would shut off and get hot with out air. On extreme hot days last summer some times it would not shut off at all in town.

Might want to change that from mph to mpg

 

[Cravenfan]

If we take the "sluggish" response aspect of the 3.21 vs 3.92 out of the equation , we can look at it from a strictly math/cost per mpg perspective.

Assumptions: 23g tank. 3.21 @17mpg vs 3.92 at 15mpg
Average miles/tank: 3.21 at 391miles/tank vs 3.92 at 345miles/tank
Decreased difference of 46miles of driving/tank

Or, about a dollar a day difference in cost between the 3.21 and 3.92.

Man the amount of forum posts and threads on this subject of gearing is mind-blowing. I have enjoyed the 3.92 gears for the sheer fun of driving it and will occasionally tow a snowmobile trailer. It is also what came on my truck. So, being transparent, If it came with a 3.21, that is what I would have ended up with. I probably still would have been very happy.

Everyone drives a different route, different pedal response, etc. We are all comparing apples and oranges. "EPA estimated" is a joke anyway, the EPA doesn't do the testing, they just say how to do the test. Who drives at 55 mph on the highway? Not me...if the highway speed is 55, I go 64 mph. We have a section of highway here that is 75 mph, I go 84 mph and my gas mileage is horrible there. But, I get to camp faster.

Anyway, this topic won't go away, but I think everyone should throttle down on the "poor gas mileage" talk and understand you are buying a Hemi V8 for the impact it makes. If you were looking for a truck with good gas mileage, you should probably have shopped elsewhere. I know why my gas mileage is bad, because I love to jump on it from light to light, down any straightaway, etc. I also think it will improve slightly over time, once we get back into summer gas blend, etc. But, my style of driving probably won't change much.

Not trying to be disrespectful to the audience, but just my 2 cents...or more like my $1 a day. Be happy the guy next to at the light is scared...

 

[Jack]

Check out my post.

An Engineer's Ultimate Guide To 3.21 VS 3.92 Axle Ratio

I hope this post will help to end the debate with facts and not opinions, and become THE post people refer to those who are having a hard time deciding. You already know that 3.92 is better for towing, and 3.21 gets better fuel economy, so I will talk about what you might not know Bottom line...

5thgenrams.com

 

[Ramit392]

Might want to change that from mph to mpg

haha....thanks.

 

[kraftwerx]

I have been shopping for a 5th gen for over 18 months and keep landing on the factory order option to get exactly what I want. Most of the frustration has been with the MFT, but now given the 0% offer, and assuming the dealer is incentivized to make a deal, the only gap on one that I found is the RAR.

I definitely want the 3.92 and am okay paying more for aftermarket if that plus the available truck is less than custom ordering, so my question is whether I can change this with an aftermarket upgrade and have the effective towing of the factory order.

Some questions are:

• Is there an aftermarket kit available?
• Am I correct that with 4x4, I actually have to do both the front and rear, thus doubling the cost?
• Does the LSD that comes with this truck get in the way of the upgrade?
• Is the transmission the same regardless of the stock RAR? I've seen some posts that might indicate the gearing is changed depending?
  • If not, am I impacted by a 3.21 tuned tranny now pushing 3.92?
• Most importantly, could I get into a lengthy debate my local equipment rental yard or CHP that somehow is able to know what the factory tow capacity was vs my upgraded capacity?

I'm sure I can come up with more, but that should cover the major ones.

Thanks, Erik