F450 vs Ram 3500 DRW tow vehicle

ShinerBock wrote:

4x4ord wrote:

ShinerBock wrote:

4x4ord wrote:
^^^^ The thing is pulling an 18000 lb rv down the highway at 70 mph is light work. At 2000 rpm the 2020 Powerstroke can make approximately 380 HP. Even if you have an RV that requires 180 HP to tow it down the highway at 70 mph, why would you want your truck geared such that the engine revs to an rpm where it is able to produce over double the required HP? 4.30 gears are too deep for us RVers, especially when they are offering us a 10 speed transmission. If you have a 10 speed transmission and 3.55 gears and find yourself towing against a wind or in light hills and find the transmission is dropping out of 10th too often for your liking, you can simply lock out 10th gear.

The 10th gear in the 10R140 is the same as 6th in my 68RFE. I also have 3.42 gears. I get better fuel mileage if I put mine in 5th(which is about 8th in the 10R140) towing my 14k trailer. I used to tow it in 6th down to the same 160 mile route to the coast(which is mostly flat) the first few years I had the truck. About three years ago I started towing it in 5th, and my app calculated numbers fuel mileage shows that I averaged better fuel mile towing in 5th than I do 6th.

My truck can easily tow it in 6th, but I noticed that I had to put the engine under more load than I did in 6th. My fuel rail pressure pressure was much higher on average along with my EGT's and boost in 6th than 5th. Line pressure in my trans is lower to since it is not trying to keep the clutch of such a low gear together. This inturn lower trans temps.

I've never seen a brake specific fuel consumption graph that supports what you're claiming on a stock engine. Gearing up and throttling down saves fuel under light load conditions. I wonder if your aftermarket program is over fueling at low rpm and high throttle position to produce high torque at the expense of engine efficiency?

My truck was tuned withing 30k miles and towed with it for at least one year before I switched to towing in 5th. My brother also has a 2014 just like I do that was 100% as of a few weeks ago and saw the same results I did. Cummins power spec states that the 6.7L is most effeicnt between 1,800 and 2,000 rpms when towing. That is what what Cummins tuned/design the cam/turbo and rest of the engine for. Can't speak for the Powerstroke though since every engine is tuned/designed differently.

I remember Cummins used to publish this kind of data below, but I haven't seen one of these charts below(for the 5.9L) in a long time. I will try to find one for the 6.7L. I would wager it would show some similar as below.

This is very useful info but it needs to be interpreted properly. So the 5.9 was capable of achieving its best fuel economy at 2000 rpm BUT that is under heavy load. Under heavy load it was able to make 175 hp at 2000 rpm. If its fuel consumption was measured at 2000 rpm and it was only loaded to 50% of its capability it certainly would have been using more fuel than .334 lbs per hphr. I'm talking about slowing an engine down under light load conditions to improve fuel economy.
If that old Cummins had a demand on it of 80 hp, I would call that a light load, It could easily produce 80 hp at 1500 rpm and I would be willing to bet it would achieve better fuel economy producing 80 hp while running at 1500 rpm than it would running 2000 rpm with a 80 hp demand on it.

The new Powerstroke is a totally different animal. At 1600 rpm it can produce 320 HP.... 380 hp at 2000 rpm. I am saying 175 hp demand on a new Powerstroke engine qualifies as a very light load. It doesn't need anywhere near 2000 rpm to produce 175 HP. In other words 175 HP to the new Powerstroke is like 80 HP was to the old 5.9 Cummins.

And I think it is very few RVs that even require 175 HP to pull them down the highway at 70 mph. So I'll stick with my claim that 4.30 gears are not the right gears for RVers wanting a new Powerstroke. If you want a F450 for the wide front axle it is understandable but the 4.30 axle unfortunately comes with it.

IdaD wrote:
How fast are you typically towing when you see better mileage in 5th? We're taking the camper out this weekend but we'll mostly be on the freeway so I'll probably be running at around 72-73 MPH.

Generally run 5th between 65-71. Anything above 75 mph and above is 6th. It mainly has to do with the rpm. I try to keep it between 1,800 and 2,000 rpm. Between 70 and 75 is kind of a grey area because the rpms are too high in 5th and still low in 6th with my 34 inch tires.

How fast are you typically towing when you see better mileage in 5th? We're taking the camper out this weekend but we'll mostly be on the freeway so I'll probably be running at around 72-73 MPH.

4x4ord wrote:

ShinerBock wrote:

4x4ord wrote:
^^^^ The thing is pulling an 18000 lb rv down the highway at 70 mph is light work. At 2000 rpm the 2020 Powerstroke can make approximately 380 HP. Even if you have an RV that requires 180 HP to tow it down the highway at 70 mph, why would you want your truck geared such that the engine revs to an rpm where it is able to produce over double the required HP? 4.30 gears are too deep for us RVers, especially when they are offering us a 10 speed transmission. If you have a 10 speed transmission and 3.55 gears and find yourself towing against a wind or in light hills and find the transmission is dropping out of 10th too often for your liking, you can simply lock out 10th gear.

The 10th gear in the 10R140 is the same as 6th in my 68RFE. I also have 3.42 gears. I get better fuel mileage if I put mine in 5th(which is about 8th in the 10R140) towing my 14k trailer. I used to tow it in 6th down to the same 160 mile route to the coast(which is mostly flat) the first few years I had the truck. About three years ago I started towing it in 5th, and my app calculated numbers fuel mileage shows that I averaged better fuel mile towing in 5th than I do 6th.

My truck can easily tow it in 6th, but I noticed that I had to put the engine under more load than I did in 6th. My fuel rail pressure pressure was much higher on average along with my EGT's and boost in 6th than 5th. Line pressure in my trans is lower to since it is not trying to keep the clutch of such a low gear together. This inturn lower trans temps.

I've never seen a brake specific fuel consumption graph that supports what you're claiming on a stock engine. Gearing up and throttling down saves fuel under light load conditions. I wonder if your aftermarket program is over fueling at low rpm and high throttle position to produce high torque at the expense of engine efficiency?

My truck was tuned withing 30k miles and towed with it for at least one year before I switched to towing in 5th. My brother also has a 2014 just like I do that was 100% as of a few weeks ago and saw the same results I did. Cummins power spec states that the 6.7L is most effeicnt between 1,800 and 2,000 rpms when towing. That is what what Cummins tuned/design the cam/turbo and rest of the engine for. Can't speak for the Powerstroke though since every engine is tuned/designed differently.

I remember Cummins used to publish this kind of data below, but I haven't seen one of these charts below(for the 5.9L) in a long time. I will try to find one for the 6.7L. I would wager it would show some similar as below.

ShinerBock wrote:

4x4ord wrote:
^^^^ The thing is pulling an 18000 lb rv down the highway at 70 mph is light work. At 2000 rpm the 2020 Powerstroke can make approximately 380 HP. Even if you have an RV that requires 180 HP to tow it down the highway at 70 mph, why would you want your truck geared such that the engine revs to an rpm where it is able to produce over double the required HP? 4.30 gears are too deep for us RVers, especially when they are offering us a 10 speed transmission. If you have a 10 speed transmission and 3.55 gears and find yourself towing against a wind or in light hills and find the transmission is dropping out of 10th too often for your liking, you can simply lock out 10th gear.

The 10th gear in the 10R140 is the same as 6th in my 68RFE. I also have 3.42 gears. I get better fuel mileage if I put mine in 5th(which is about 8th in the 10R140) towing my 14k trailer. I used to tow it in 6th down to the same 160 mile route to the coast(which is mostly flat) the first few years I had the truck. About three years ago I started towing it in 5th, and my app calculated numbers fuel mileage shows that I averaged better fuel mile towing in 5th than I do 6th.

My truck can easily tow it in 6th, but I noticed that I had to put the engine under more load than I did in 6th. My fuel rail pressure pressure was much higher on average along with my EGT's and boost in 6th than 5th. Line pressure in my trans is lower to since it is not trying to keep the clutch of such a low gear together. This inturn lower trans temps.

I've never seen a brake specific fuel consumption graph that supports what you're claiming on a stock engine. Gearing up and throttling down saves fuel under light load conditions. I wonder if your aftermarket program is over fueling at low rpm and high throttle position to produce high torque at the expense of engine efficiency?

4x4ord wrote:
^^^^ The thing is pulling an 18000 lb rv down the highway at 70 mph is light work. At 2000 rpm the 2020 Powerstroke can make approximately 380 HP. Even if you have an RV that requires 180 HP to tow it down the highway at 70 mph, why would you want your truck geared such that the engine revs to an rpm where it is able to produce over double the required HP? 4.30 gears are too deep for us RVers, especially when they are offering us a 10 speed transmission. If you have a 10 speed transmission and 3.55 gears and find yourself towing against a wind or in light hills and find the transmission is dropping out of 10th too often for your liking, you can simply lock out 10th gear.

The 10th gear in the 10R140 is the same as 6th in my 68RFE. I also have 3.42 gears. I get better fuel mileage if I put mine in 5th(which is about 8th in the 10R140) towing my 14k trailer. I used to tow it in 6th down to the same 160 mile route to the coast(which is mostly flat) the first few years I had the truck. About three years ago I started towing it in 5th, and my app calculated numbers fuel mileage shows that I averaged better fuel mile towing in 5th than I do 6th.

My truck can easily tow it in 6th, but I noticed that I had to put the engine under more load than I did in 6th. My fuel rail pressure pressure was much higher on average along with my EGT's and boost in 6th than 5th. Line pressure in my trans is lower to since it is not trying to keep the clutch of such a low gear together. This inturn lower trans temps.

^^^^ The thing is pulling an 18000 lb rv down the highway at 70 mph is light work. At 2000 rpm the 2020 Powerstroke can make approximately 380 HP. Even if you have an RV that requires 180 HP to tow it down the highway at 70 mph, why would you want your truck geared such that the engine revs to an rpm where it is able to produce over double the required HP? 4.30 gears are too deep for us RVers, especially when they are offering us a 10 speed transmission. If you have a 10 speed transmission and 3.55 gears and find yourself towing against a wind or in light hills and find the transmission is dropping out of 10th too often for your liking, you can simply lock out 10th gear.

Grit dog wrote:


I don't disagree with you, theoretically, however, realistically, unless all the online calculators are wrong (and I'm not busting out the statics and dynamics book tonight), 24-28k gross, 96 sf frontal area at 70mph is average around 230-250hp to overcome air drag and rolling resistance.
That's average. No head or side winds, no grades, etc.
Yes, the new Powerstrokes make impressive HP down low, but it's not quite as rosy as it seems, IMO.

And you're talking roughly 1600rpms vs 2000rpms on a F450 with 4.30s vs 3.55s. You're not going to hold 10th gear with 3.55s with any large trailer at 70mph except in a vacuum.
So down it shift a gear or 2 and then pops back up when the wind stops for a second, then down when you go up the other side of a dip in the road and back up when you go down the dip, so then yo ulock it in 8th gear and there you are...

Bobtail or light trailers, sure 3.55s will hold top gear all day, likely. And drop a couple/3/4 gears for the BIG loads.

I agree that deep gears aren't needed except for BIG loads and even at that, with 10 cogs, there's a gear for every condition.

But if you're tugging around the stuff that requires a 450 chassis, why not have the most snort behind the skinny pedal?

Bet you're not saving appreciable fuel unless running light weight, but then that's not what the truck is made for with 4.30s although it'll still do 10x better than my old 6 speed with higher gears.

I agree. If the truck is going to loaded most of the time or even half of the time then it is best to get the shortest gear ratio possible for better fuel economy and less stress due to higher cylinder pressures on the engine. Not only that, but the performance factor is another abstract benefit as well. However, if it is rarely going to tow then taller gears will be the best option for fuel economy. I would like to think that if someone is going to step up to an F450, then they are likely going to pulling a load behind it most of the time. Otherwise they would get an F350.

Grit dog wrote:

4x4ord wrote:

Grit dog wrote:
So 4x4ord has a point with the overall gearing (Trans od ratios and rear gears) and power the engine puts out.
But What he is actually saying is the 4.30 geared Ford doesn’t “need” that low of gears and there may be a small fuel consumption advantage to the taller gears when cruising empty. I doubt you’d see any measurable difference hooked up heavy. Any small efficiency on the engine end of lower rpms will still have to drive through taller finals.
Likely a wash.
My old Mega is a good example of what I’m saying above. Even with taller than stock tires, the shallow OD ratio puts it at 2000rpms just a little over 60 mph and cruising at 85mph is like 2600-2700 rpms. Truck will do it all day long but I’ve driven similar trucks with a deeper OD and it seems the fuel economy is not much different.
So many conditions affect fuel economy, the gearing is only a small part of the equation.

Regardless of what the president of the Ram mafia says, by the numbers a new 4.30 450 Powerstroke IS king of the hill right now on all fronts when it comes to capability.

Tests have been conducted on Agricultural tractors by Nebraska Tractor Tests and have shown that when 1/2 of rated HP is needed a tractor will burn nearly 30% less fuel running the engine at 80% rated engine rpm vs running at full rated rpm. The same is likely true of the Powerstroke. If 235 HP were needed to pull a very heavy trailer it should be expected that running at 2080 rpm would burn about 70% the fuel vs running the engine at 2600 rpm while running the same road speed. When less HP is required (such as what is required to pull a heavy RV .... 110 - 140 HP)running the engine at 1600 rpm could potentially save significantly more fuel.

I don't disagree with you, theoretically, however, realistically, unless all the online calculators are wrong (and I'm not busting out the statics and dynamics book tonight), 24-28k gross, 96 sf frontal area at 70mph is average around 230-250hp to overcome air drag and rolling resistance.
That's average. No head or side winds, no grades, etc.
Yes, the new Powerstrokes make impressive HP down low, but it's not quite as rosy as it seems, IMO.

And you're talking roughly 1600rpms vs 2000rpms on a F450 with 4.30s vs 3.55s. You're not going to hold 10th gear with 3.55s with any large trailer at 70mph except in a vacuum.
So down it shift a gear or 2 and then pops back up when the wind stops for a second, then down when you go up the other side of a dip in the road and back up when you go down the dip, so then yo ulock it in 8th gear and there you are...

Bobtail or light trailers, sure 3.55s will hold top gear all day, likely. And drop a couple/3/4 gears for the BIG loads.

I agree that deep gears aren't needed except for BIG loads and even at that, with 10 cogs, there's a gear for every condition.

But if you're tugging around the stuff that requires a 450 chassis, why not have the most snort behind the skinny pedal?

Bet you're not saving appreciable fuel unless running light weight, but then that's not what the truck is made for with 4.30s although it'll still do 10x better than my old 6 speed with higher gears.

Let's take a look at the numbers from a little different vantage point. Here is the test results of a Cummins ISX 15 liter engine:


Running at peak HP it was able to operate at 600 maximum HP while burning 225 lbs of fuel per hour .... 0.37 lbs of fuel per HPhour. A pick up truck running a part load is not going to be able to get that kind of fuel economy but just for kicks lets say pulling a heavy RV a pick up consumes 0.4 lbs per HpHr.

If at 70 mph you are getting 8 mpg in your pick up pulling a heavy RV you're probably not going to be thrilled with your mileage but even so you'll only be burning 8.75 gallons of fuel per hour. There is about 7.2 lbs of fuel in a gallon so 8.75 x 7.2 = 63 lbs of fuel per hour which means the truck was producing 63/.4 = 157 HP.

I think many people believe that only rpm effects fuel efficiency which is true if the load is the same at all rpms, but that isn't the case when the load on the engine is different especially when you add different gear ratios into the mix.

Basically, you need torque to move the wheels and to counteract the forces pulling you back. You increase torque two ways, more engine load(fuel) or gear multiplication. A torque converter also increases torque, but that is essentially gear multiplication in hydrophilic form.

Keep in mind, that load does not necessarily mean rpm increase. An engine at 1,800 rpm can make partial, half or the max amount of power it can possibly make at that rpm depending on the amount of load(fuel being injected) is being placed upon it. The more power you need.want to make at that rpm requires more fuel since it is more of load being placed on the engine.

Anything you tow requires a certain amount of torque(force) to counter act the forces that want to pull you back. The amount of force wanting to pull you back is always changing even when the weight stays the same such as going up/down hills or high drag scenarios. Basically, you must have enough torque to overcome these forces in order to perform the work at a certain speed(aka make horsepower). If you don't have enough torque then your truck will keep downshifting to greater torque multiplication and more engine torque until it has enough torque to overcome this and make horsepower.

So getting back to the fuel thing. Say you are pulling a trailer that is pulling you back with 1,200 lb-ft of force. You can can easily pull this load in 5th at 1,900 rpm or 6th gear at 1,600 rpm. Even though 5th puts you at a higher rpm, it has greater torque multiplication and more of the torque needed to overcome this 1,200 lb-ft is coming from this gear torque multiplication rather than adding more load to the engine. In 6th gear, even though it is turning at less rpm, the truck has less torque multiplication and therefor more load(more fuel) is placed on the engine to make up the torque needed to overcome this 1,200 lb-ft of force pulling you back. Basically, you are planting your foot to the floor in 6th to get full load/max effort out of the engine and half throttle or half load in 5th so you are not needing max effort at that rpm from the engine in 5th therefor less fuel is needed.

When there is very little force pulling you back and it takes very little effort or load from the engine to overcome this force, then 6th gear is the optimal choice for fuel efficiency. All this applies to different rear gear ratios as well.