3.21. vs 3.92 gear

[Goatmann]

One other thing I thought about this morning is how much would a tonneau cover help with fuel economy. I'd expect on the highway it could matter.

with the improved aerodynamics of the 5th gen, i don't think the addition of a tonneau cover would help fuel economy much at all.
i have one on my truck for looks and out of sight/out of mind storage. if i get a 10th of a MPG with it on wonderful.

 

[UnLimited]

Towing today about 350 miles, 8k camper - sadly 9.2 mpg and running 65-70, fairly flat.

 

[go-ram]

TFL Truck tested a Limited 4x4 with eTorque and 3.92 rear end up the "Ike Gauntlet" (Eisenhower Grade) and it got 4.7 MPG towing 7,000 lbs flat-out (maintaining 60 MPH up the full two miles of 7% grade).
https://www.tfltruck.com/2018/11/20...orlds-toughest-towing-test-ike-gauntlet-2019/


Motor Trend's Limited 4x4 eTorque with 3.92 rear end got fairly decent fuel economy in MT's "Real MPG" testing (18.7/22.6/20.3 MPG).
https://www.motortrend.com/news/ram-1500-2019-truck-of-the-year/
Most interestingly, the 5.7 L Hemi eTorque with 3.92 rear end got 3.2 MPG better than the comparable 3.6 L V6 with its 3.55 rear end ratio.

 

[Gman]

Most interestingly, the 5.7 L Hemi eTorque with 3.92 rear end got 3.2 MPG better than the comparable 3.6 L V6 with its 3.55 rear end ratio.

It's all about the torque when you're towing. That's why diesels do so well.

 

[ExcursionDiesel]

Not getting anything near that on mine...

Just took a trip from FL to WI
75mph and cruise control, 87 octane
15 mpg was average
14 mpg was worst tank
16 mpg was best tank

Have to add up the info for the ride back..

The 3.92 gets better in town than on the highway. With a light foot, I've gotten over 20mpg in town. I have the eTorque Hemi. Above 60mph, you won't see 20mpg. It drops to <16mpg at 75+.with the 4x4 with ORG.

 

[SpeedyV]

The 3.92 gets better in town than on the highway. With a light foot, I've gotten over 20mpg in town. I have the eTorque Hemi. Above 60mph, you won't see 20mpg. It drops to <16mpg at 75+.with the 4x4 with ORG.

Having grown up in a small town, I can buy that. Now that I live in a major city, it's rare to spend much time at 45 mph or below anywhere but in my neighborhood. We have highways everywhere here "in town"!

 

[ExcursionDiesel]

Towing today about 350 miles, 8k camper - sadly 9.2 mpg and running 65-70, fairly flat.

That's typical. Only a diesel would improve that number much. Campers are like dragging a parachute through the air and 8k isn't a light load.

 

[ExcursionDiesel]

Having grown up in a small town, I can buy that. Now that I live in a major city, it's rare to spend much time at 45 mph or below anywhere but in my neighborhood. We have highways everywhere here "in town"!

I live near a small city of 80k. Most roads are 40mph in town. I've seen as low as 12mog when driving aggressively and as high as 20mpg when really focusing on achieving the highest instantaneous mpg readings.

Hypermiling is a skill that can be learned.
https://m.wikihow.com/Hypermile

I don't drive that way all the time but with eTorque and MDS, the truck CAN achieve much higher mpg's than a typical driver will see BELOW 50 MPH. I did it just to see what the truck would do. Highway mpg's above 60mph with the 3.92 4x4 with Off Road Group are not so good no matter the technique. The motor is operating above its most efficient RPM and the aerodynamics of a truck increase the engine load more as speed goes up.

 

[Gondul]

Highway mpg's above 60mph with the 3.92 4x4 with Off Road Group are not so good no matter the technique. The motor is operating above its most efficient RPM and the aerodynamics of a truck increase the engine load more as speed goes up.

Fully aware that mpg would be lower than claimed due to the 3.92, 4x4, and ORG, somewhat disappointed it is *that* low... just need to find that sweet spot and figure out the variables.

I haven't had a chance to finish the calculation for the trip back, but I was fighting a 20+mph head wind... once I cleared that and got onto level(ish) terrain looks like I got about 17 mpg using 89 octane.

 

[Ramit392]

The 3.92 option adds roughly 3000 pounds of towing capacity. Is the only difference between the two (3.31 vs 3.92) just the ratio?

That seems like a lot of difference in weight. Brakes, bearings and axles the same?

I would think it's more important to stop while towing than it is to start. If the 3.92 can tow that much weight safely, wouldn't the 3.21 be just as safe? Might take a while to get going but can handle the weight just the same.

I made a slight mistake in my post #13 comparing 3.92 to 3.21. There is a difference from 3.21 to 3.92 if your pulling over 7000 lbs or so,but comparing the 3.55 to the 3.92 its very minimal. Its most likely why they stopped the 3.55 production when the 8 speeds came out.

You are correct on the actual truck differences in my opinion about the 3000 lbs comparing the 3.92 to the 3.21. That extra 3000 lbs is needed if pulling much over 6500 lbs. The "take off" mostly using the extra torque to start makes it a little easier. But,as you said Stopping is needed or "pushback". which is assisted by two things "Pushback" on the heavy weight going down grades,hills,etc.from the lower gearing and of course by the electronic trailer brakes from the trailer, lighter weight trailers have Surge brakes which help to stop but no "Pushback".
The upper weights of 6500 lbs. or more with the 3.92 helps with quite a bit to manage by getting the "pushback" from the Truck against the trailer. IMO 6500 lbs. or under there would be minimal difference with 3.21 vs. 3.92 from my past experiences with both gears if that makes sense. There is heat differences generated from each gear from pulling as well.

 

[Ramit392]

Fully aware that mpg would be lower than claimed due to the 3.92, 4x4, and ORG, somewhat disappointed it is *that* low... just need to find that sweet spot and figure out the variables.

I haven't had a chance to finish the calculation for the trip back, but I was fighting a 20+mph head wind... once I cleared that and got onto level(ish) terrain looks like I got about 17 mpg using 89 octane.

At 5300 Miles I get combination driving mostly the open road 90% around 18 mpg. Straight out on the road around 19. If I were to drive in town all the time or in large city...I would bet it gets about 15 MPG unless I get heavy footed during take offs....lol.

 

[Ramit392]

My lifetime (~2,300 mi) average is just over 15 mpg with a "heavy" truck and 3.92 ratio. Interestingly, I was running 93 octane (out of habit) and seeing north of 16 mpg on my last couple of tanks, whereas I switched to 89 octane this tank and am seeing just under 15 mpg. I'll keep an eye on this and see if it's just an anomaly, or if the computer needs time to adjust, or if my engine just happens to be a little high on the compression side and does better on premium.

After I hit the 4500 mile side with 89 and usually about 63 mph on the road 90% of the times I have increases to about 18 mpg If I go over 65 mph most of the drive each time it drops to about 17. Before the 4500 miles I was in about the same mpg as yourself. Not done premium yet will have to reset and try it see what happens. It seems my sweet spot is about 60 to 63 Mph.

 

[Ramit392]

Towing today about 350 miles, 8k camper - sadly 9.2 mpg and running 65-70, fairly flat.

That is not bad...when I towed the 8400lbs with my 2014 Crew cab 5.7 that was about where I would be at running 55 to 60 mph.

 

[C.E.Divine]

I'll take the 17 highway mpg from my hemi with 3.92's over the 13 mpg my cammed 5.3 Silverado with 3.73's got. My 18 hemi with 3.21's got around 18.5 on the same road. The fun factor from a dead stop is worth the mileage hit.

 

[runamuck]

I'll take the 17 highway mpg from my hemi with 3.92's over the 13 mpg my cammed 5.3 Silverado with 3.73's got. My 18 hemi with 3.21's got around 18.5 on the same road. The fun factor from a dead stop is worth the mileage hit.

I always got around 20 on the highway with my 5.3 sierra 4x4 ccsb with 3.42's and I expect to get about the same on my 4x4 ccsb laramie with 5.7 and 3.92 gears because of the two extra tranny gears on the ram. my son always gets 20 or more on his 2017 ram with same setup.

 

[Autoplay]

To follow up......From Sarasota to Miami,in a headwind last week,averaged 17.2 mpg,freeway miles,several rest stops,average mph was around 75.

On return trip,no headwind etc,18.5 mpg,freeway miles with several stop,average speed around 75.

Ran 89 octane both legs. ECO mode only seems to stay enabled,at speeds of 72 mph or lower,and/or RPM at 2100 or lower. I was rarely in eco mode,as I was driving 75-79 mph.

Flat terrain,high 70’s-low 80’s weather,no rain etc.....just a lot of headwind encountered,heading south last week.

 

[Smashy71]

I need my 3.92s here in north Idaho!

 

[Gondul]

To follow up......From Sarasota to Miami,in a headwind last week,averaged 17.2 mpg,freeway miles,several rest stops,average mph was around 75.

On return trip,no headwind etc,18.5 mpg,freeway miles with several stop,average speed around 75.

Ran 89 octane both legs. ECO mode only seems to stay enabled,at speeds of 72 mph or lower,and/or RPM at 2100 or lower. I was rarely in eco mode,as I was driving 75-79 mph.

Flat terrain,high 70’s-low 80’s weather,no rain etc.....just a lot of headwind encountered,heading south last week.

Now that I'm back in Flatistan I'm hoping my mileage will pick up...

 

[Lateralus]

I get 11 MPG towing 17,000 pounds... With my Cummins
I'm afraid to hook the Hemi to a trailer, because I know I'll be disappointed. I didn't buy it for towing, obviously...

 

[JDBob35a]

I have the 3.21 gears, pulled my boat for the first time the last two days. Fairly flat land. Boat is a 20' aluminum bass boat with 115 optimax on it, not sure of the gross weight of the rig.
Could barely tell it was back there, on the interstate running 70-75 mph it showed between 10-12 mpg. Once off the interstate and on the country back highways running 60 mph, it did 14-16 mpg. Had a very comfortable ride, and no trouble at all handling the boat. Was a big difference from pulling it with my 2013 Ford F-150 (3:55 Gears), it handled it fine but you knew you had it back there, especially from dead stop. I'm glad I went with the 3:21 gears, the boat is primarily what I pull so I think I'm going to get along with it just fine.