Sweet spot for 4.10 gears

I'm thinking the availability of 925 ft lbs means the whole range of rpm is the sweet spot eh?

Cummins12V98 wrote:
^^^^^^^ Dude where the HE!! does all that info come from??? Your brain must be very cluttered.

I tow mostly at 60 in 6th at 1,750 rpm's combined 33k average all conditions 9mpg. Any faster I get worse mileage. Any slower I get better. Less clutter in my brain. :B

Yes he has been trying to convince people that lower gearing is better for towing.

All his rambling makes him sound like an engineer. They think they know everything on paper, but in the real world things are hugely different.

People will be smart to avoid his “recommendations”!

4x4....that explanation was fantastic. Best I’ve seen on torque vs hp with regard to RPM and fuel consumption. I copied it for future reference. Thank you!

If you're burning 1 gallon per 9 miles and travelling 60 mph you're burning 6.67 gallons per hour. Because diesel contains 55 hp hrs per gallon you're engine is releasing 367 hp. If it is 40% efficient the usable power produced is 147 hp. So 147 hp is a good guess as to the average power required to tow you're trailer down the highway at 60 mph.

^^^^^^^ Dude where the HE!! does all that info come from??? Your brain must be very cluttered.

I tow mostly at 60 in 6th at 1,750 rpm's combined 33k average all conditions 9mpg. Any faster I get worse mileage. Any slower I get better. Less clutter in my brain. :B

The 2017 Powerstroke makes peak torque of 925 lb ft at 1600 rpm. At 2800 rpm where the peak hp is obtained the torque has dropped to 825 lb ft. So for every 100 rpm the engine pulls down from 2800 the torque rises by about 8 lb ft.

Based on this I would expect the engine to be able to produce about 905 lb ft of torque at 1850 rpm. This means that at 1850 rpm the engine us capable of producing about 320 crankshaft HP.

Diesel fuel contains about 55 hphrs per gallon. So for an engine to operate at 40 % efficiency and produce 320 hp for one hour it would require 14.5 gallons of diesel.

In other words the Powerstroke is capable of burning 14.5 gallons of fuel per hour at 1850 rpm.

If you are travelling 60 mph and using 14.5 gallons of fuel per hour you are getting 4 miles per gallon fuel economy.

Obviously the Powerstroke does not have to be running anywhere near 1850 rpm to produce the power required to tow a typical rv down the highway at 60 mph.

Now consider the speed the truck can travel while pulling your trailer up the type of hill you expect to encounter in your travels:

Say your combined weight is 29000 lbs. The rear wheel hp required to overcome wind and rolling resistance on level ground at 45 mph is approximately 70 Hp.

The rear wheel power required to lift the 29000 lbs up a 7% incline at 45 mph is exactly 243 rear wheel hp.

If the drivetrains is 75% efficient the engine would need to produce (70+243)/.75 HP to pull a 29000 lb truck and trailer up a 7% grade.
(70+243)/.75 = 417 hp.

It is reasonable to expect the Powerstroke to be able to produce 417 crankshaft HP so long as it is running between 2600 and 2900 rpm.

With 3.55 gears the engine would be running 2594 rpm In 3rd gear at 45 mph.

With 4.10 gears at 45 mph the transmission would be in 4th and the engine would be running at 2266 rpm. The truck with 4.10 gears would not be able to pull the hill in 4th gear so it would have to slow down to 42 mph where the driver could force a downshift and then maintain 42 mph at 2800 rpm in 3rd gear.

If you will be pulling a trailer heavier than 22000 lbs or hills steeper than 7% than 4.10 gears could possibly become advantageous over 3.55 gears. For most RVs the 3.55 gears are a better choice.

ACZL wrote:

Lynnmor wrote:
I guess you are talking about a dual rear wheel truck?

My bad.....yes.

4:10 only comes on DRW with 6.7

ACZL wrote:
I've got the bullet proof vest on, shields up and ready. If this has been asked countless times before, I apologize in advance.

What is the sweet spot for towing if truck has 4.10 gears and diesel?

Test drove a '17 F350 that had 'em and at 60 mph, rom's were around 1850+/-. 70 mph = around 2150 +/-. Obviously compared to 3.55 gears about 300 rpm's more on both accounts.

Depends on the rest of the system...

Mainly what the ICE's torque/HP curve looks like and what you plan to do...from cruise empty with just you, the driver...or towing heavy up the steeps...finally at what speed you wish to travel in the above conditions

Here is a Ford 6.0L torque/HP curve as an example...If me, I'd run between 1,500 RPMs and 2,500 RPMs...but this engine (in good condition) can go higher...or lower




Personal preferences



Here is one for a GM 8.1L gasser and I'd tow at between 1,500 RPMs and 2,500 RPMs


Click For Full-Size Image.

I have Cummins 5.9L 48RE 4 speed Auto Tranny and 4:10 differential

1950 RPM ----65MPH

Each truck will be different. To answer your question, figure 65MPH is your base line. Now what is the RPM for the configuration at 65MPH. Next you can look up the torque specs for that particular motor. Sweet spot will IMHO be between the bottom and mid point of the curve. For my Cummins torque starts at around 1650 RPM. That puts me between 1750 and 1850 RPM on the flats at 65MPH. Which is exactly where I want it to be.