Towing - Best gear ratio

[Rick3478]

You think I dont know how a modern transmission works.... Both a modern and older ones still uses clutches and gears. Modern trans use computer controlled solenoids instead of valve bodies, to more accurately control shifts. The computer analyzes throttle position, rpms, vehicle speed, current gear and the next gear (up or down), shift pressure and duration on each shift and makes adjustments as needed, to optimize the shift smoothness while minimizing clutch slippage.

The engine and transmission are the same, regardless of whether it is equipped with a 3.92 or a 3.21 rear ratio. A 3.92 equipped truck will require 3.92 revolutions of the driveshaft to accomplish one revolution of the rear tires. A 3.21 requires 3.21 driveshaft revolutions to achieve that same one tire revolution. So to cover the same piece of ground, the engine and transmission perform more work (more rpms=more work) in the form of rpms to cover the same ground. Except at idle, the 3.92 equipped truck will turn more rpms at each throttle position, in each gear and speed than its 3.21 counterpart. The 3.92 may "feel" as though it isnt working harder because of the higher rpms but in reality it is, because of the increased work to move the 3.92 truck at the same speed as the 3.21 truck. More work=more wear. Granted, not a lot more work/wearbut it is more.

It is true that while towing heavy up a grade, the 3.21 equipped truck may make a shift or 2 that the 3.92 truck doesnt and add some wear to the clutch packs, the average half ton doesnt not spend the majority of its life towing even a light load, so over the course of its life, the avearge half ton will experience its most wear and tear empty.

And with that, I am out of this discussion. You all can continue your chest thumping without my input.

Work = Speed * Force. In rotational terms, Horsepower = RPM * Torque. Same amount of work regardless of gear ratio. But something in the drivetrain has to do gear reduction to match engine speed to road speed. At the upper end of load range, it makes sense to allocate more of that job to the ring & pinion.

 

[IvoryHemi]

more rpms=more work

The 5.7L Hemi makes more torque at higher RPM.

More torque = less work

 

[Bt10]

Let’s look at this from the back side. Do you want to buy a 10 yr old truck that pulled max weight with 3.21s, or the same truck with 3.92s that never towed, same miles? This is what everyone knows as “work”, ie high throttle position with low rpm creating pressure, creating wear; vs light throttle with slightly higher rpm creating light load and less wear.

 

[Nsleone]

Hi @teamroper60 please look at this,

https://www.ramtrucks.com/content/dam/fca-brands/na/ramtrucks/en_us/towing/Ram_LD_DT_Trailer-Tow-Weight-Chart_MY21_R1.pdf

Every single configuration has a higher tow capacity when equipped with 3.92, which discredits your argument that 3.92’s have more wear and have to work harder when towing. If that were true they would not be rated to tow more. Every single line of trucks use lower gear ratios to tow more, there’s no arguing that.

If you are trying to argue 3.21 vs 3.92 when not towing, you’re in the wrong thread.

 

[Idahoktm]

Hi @teamroper60 please look at this,

https://www.ramtrucks.com/content/dam/fca-brands/na/ramtrucks/en_us/towing/Ram_LD_DT_Trailer-Tow-Weight-Chart_MY21_R1.pdf

Every single configuration has a higher tow capacity when equipped with 3.92, which discredits your argument that 3.92’s have more wear and have to work harder when towing. If that were true they would not be rated to tow more. Every single line of trucks use higher gear ratios to tow more, there’s no arguing that.

If you are trying to argue 3.21 vs 3.92 when not towing, you’re in the wrong thread.

Actually, 3.92 is a lower gear ratio than 3.21.

 

[Nsleone]

Actually, 3.92 is a lower gear ratio than 3.21.

Shhhhh it never happened I don’t make mistakes I’m a robot

 

[Nsleone]

Actually, 3.92 is a lower gear ratio than 3.21.

Yeah I originally was going to say that trucks that use higher gears tow less and then I flipped the one word and forgot the other lol thanks for the catch

 

[theblet]

3.92 is a lower gear, which will keep your engine from straining at much to get your load moving, and keep it moving. Imo, reduces wear on the mechanical components of the engine. The compromise is higher rpms during regular driving. Not an engineer, just what I’ve experienced. Pick the gear that suites your needs.

 

[gabriel86]

My question is will 3.92 gears allow the truck to shift into a higher gear which in return would drop the rpms. I only like tow my 30 ft. TT around 60 mph. With my 3.21 gears it sits in 5th and 6th mostly 5th never make into 7-8th. Will 3.92 give me the edge to make it into overdrive and quiet the truck som.

 

[Bt10]

My question is will 3.92 gears allow the truck to shift into a higher gear which in return would drop the rpms. I only like tow my 30 ft. TT around 60 mph. With my 3.21 gears it sits in 5th and 6th mostly 5th never make into 7-8th. Will 3.92 give me the edge to make it into overdrive and quiet the truck som.

No, the truck will stay in whatever gear to rev the engine to make whatever power you are requesting with your foot and holding the speed. Whether that's 5th thru a 3.21 or 7th thru a 3.92, you'll be revving the same.

 

[Rick3478]

My question is will 3.92 gears allow the truck to shift into a higher gear which in return would drop the rpms. I only like tow my 30 ft. TT around 60 mph. With my 3.21 gears it sits in 5th and 6th mostly 5th never make into 7-8th. Will 3.92 give me the edge to make it into overdrive and quiet the truck som.

There's about one gear difference between 3.21 and 3.92. If you're never getting into 7 with 3.21, you'll never get into 8 with 3.92 and be about the same RPM. A possible advantage is if you can get it to stay in 6, that's direct drive in the transmission, which will cause less heat and wear. Also less torque load on driveshaft u-joints with 3.92.

 

[Casull]

No. Start off on a 10 speed bicycle in 1st gear or 10th gear.

No, that would be start off in 1st gear or 2nd gear. Can't stand hyperbole.

 

[theblet]

My question is will 3.92 gears allow the truck to shift into a higher gear which in return would drop the rpms. I only like tow my 30 ft. TT around 60 mph. With my 3.21 gears it sits in 5th and 6th mostly 5th never make into 7-8th. Will 3.92 give me the edge to make it into overdrive and quiet the truck som.

Won't help with cruising speed, but 3.92s would help get your truck moving better from a stop.

 

[TampaLaramie]

I have a 26’ 5500-pound dry weight camper. It weighs around 7k loaded. I’m gentle accelerating while towing from a stop. But the ED doesn’t have to work or scream to make power. I use 7th gear very often at 65-70. The truck will let me if I let off, it shifts, and it will hold it. Other times it will shift into 7th in its own. I think this truck handles it very well.

Towing the camper I get between 20-24mpg. I do live in Florida where there aren’t hills or mountains, but that still beats 10-15 for other trucks/engines. Not towing I get 22-24 stop and go, 32 highway.

There’s another thread on here that has info about this, one thing that stuck out to me is the 3.21 gears give you an extra gear from the tranny. So trucks that have the 3.92, 8th gear is like 7th with the 3.21.

The 8 different gear ratios resolve the problem of the only focus needing to worry about what your pumpkin ratio is.

Oh and side note, I will strongly support the Equalizer WDH. I have one and it’s great. Complete difference from an old-school Reese WDH that used brake pads that you torqued down on the sway bars. ****ty design.

 

[Rick3478]

Let’s look at this from the back side. Do you want to buy a 10 yr old truck that pulled max weight with 3.21s, or the same truck with 3.92s that never towed, same miles? This is what everyone knows as “work”, ie high throttle position with low rpm creating pressure, creating wear; vs light throttle with slightly higher rpm creating light load and less wear.

Alternate view, engine is more efficient at high throttle so you get the job done with even fewer revolutions than the difference in gear ratio would dictate, therefore less wear.

 

[IvoryHemi]

Won't help with cruising speed, but 3.92s would help get your truck moving better from a stop.

also better engine braking for stopping.

 

[irishwake63]

I dont get it I am getting crappy mileage when towing I have many Rams and last truck was a 21 F150 with the 2.7 towing my 6500k trailer(fully loaded) I have always got 10-11 MPG on past trucks my new 22 1500 gets 6-7 with same trailer nearly 1900 lb payload 5.7 with the 3.21 E rated 10 ply tires and run 62-65 mph with or without tow mode

 

[Rickyrocket]

my 2020 gets 9mpg towing a 6500 lb trl. With 5.7 and 3.21s

 

[PurpleRT]

Thats towing for you. Without a turbo you can’t be surprised by the low MPG just the name of the game.


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[tech97elec]

On this topic bc i just got back from 750 miles trip picking up my new 8.5 x 20 EMPTY enclosed trailer, 7 foot tall, 3200#.

My truck is 2022 1500 Limited Longhorn, 5.7 e torque with 3.92 gears, 33 gallon. We towed 95 north, GA to MD, mostly flat but some hills for sure. Got 7 mpg. Very disappointed. Engine has plenty of power, but stuck in 5th, 6th most of the time, even level or downhill stretches, fuel tank empties less than 250 miles. Tried to stay at 70mph most times. Checked trailer hub temps every stop.... just warm, so all good there. Future trips will be to West VA, mostly mountains.

(My 2012 Nissan NV2500 with 5.6 V8 towing open trailer w car weighed 5000# and I got 10-12 mpg. Less windage I know.)

Curious what MPG is your hemi getting towing a TT or enclosed car trailer? Is 7 about right? Thinking i shouldve gotten 2500 with diesel bc my now empty trailer will gain about 2,000#'s shortly with quads, etc.