4:10 or 3:73 ?

[TxGearhead]

Possible upgrading to Ram dually. I'm pulling 12,500# gvw with SRW and 3.42 rear end. Usually lock 6th gear out. Plan is to move up to new 15,000# gvw 5th. Not sure if I want to get 4.10 or 3:73.
Whata ya think?

[rhagfo]

TxGearhead wrote:
Upon further reflection....
I sure like my 3.42!

It's all iffy what we are going to do. I would like to get that last RV. But I'm not shelling out good money for it to sit outside and bake in Texas sun. Our son just closed on his country acreage. We'll see how his schedule is for building a barn and pivot this around him.

If you are only towing a bit over 12,000# stick with the current TV. I tow almost that much with my 2001 2500 5.9 with 3.55's and with 5 speed stick use 5th all the time.

[justme]

4x4ord wrote:

justme wrote:
There is no easy answer, but if you pull a heavy load most of the time the lower gear is the better. Otherwise the high gear is prefer for light loads and intermittent heavy loads. Fuel mileage and engine wear (piston travel/mechanical stress) is important for long term wear and tear. For my experience the higher gears are preferred because I pull a heavy load intermittently. I pull a 165000GVW trailer with a F350 SRW with a 3.5 rear end. I have 40k miles on the trailer and 90K miles on the 2012 diesel truck. The TV pulls very well and if the tranny starts hunting between 5th an 6th gear, I lock it in 5th and everything is good. The torque on the F350 is fantastic and pulls grades very well. I see no need for 4:11 rear end.... I average 12mpg pulling 20mpg not pulling. I set the cruise control to 60 mph pulling and 75mph not pulling.

That is very good fuel economy. Do you have a programmer on it? I might see 20 mpg empty if the stars are all aligned and I don't exceed 60 mph. Pulling I'm more like 9 - 10 per US gallon. My overall average mileage for how I use the truck is 12.5 mpg.

No everything is stock. I traveled from California to the east coast and averaged 12.2 mpg for the entire trip. When I travel not pulling from Florida to Connecticut I get 20.1 mpg average for the whole trip. I use cruise control where possible and I use an additive to increase the Ctane rating of the diesel. The Ctane and quality of the fuel is noticeable. Most states mandate a Ctane of 40 while California mandates a Ctane of 50. So Californians should see a better mpg. If you use B20 you will see a significant decrease in mpg. If you use B5 in a good brand you will see an improvement. One time I had 23 mpg from fuel I bought on the NJ turnpike which is best mpg I have ever had. I wished I lived closer to that pump. Most of the truck stops are 40 while the do vary between 40 to 45 depending on the batch. Then of course environmental conditions and driving habits plan a big role 🙂

If you use the power that your engine is capable of you will greatly decrease the economy. I some times wonder if the newer Fords that have increase their torque and H.P. would be more of a challenge to get better mpg than my 2012. That power increase may be nice but I could imagine that it will gabble up fuel much faster when one demands that power. My truck has all the power I need and I am happy with it, but I am jealous as well 🙂

[4x4ord]

justme wrote:
There is no easy answer, but if you pull a heavy load most of the time the lower gear is the better. Otherwise the high gear is prefer for light loads and intermittent heavy loads. Fuel mileage and engine wear (piston travel/mechanical stress) is important for long term wear and tear. For my experience the higher gears are preferred because I pull a heavy load intermittently. I pull a 165000GVW trailer with a F350 SRW with a 3.5 rear end. I have 40k miles on the trailer and 90K miles on the 2012 diesel truck. The TV pulls very well and if the tranny starts hunting between 5th an 6th gear, I lock it in 5th and everything is good. The torque on the F350 is fantastic and pulls grades very well. I see no need for 4:11 rear end.... I average 12mpg pulling 20mpg not pulling. I set the cruise control to 60 mph pulling and 75mph not pulling.

That is very good fuel economy. Do you have a programmer on it? I might see 20 mpg empty if the stars are all aligned and I don't exceed 60 mph. Pulling I'm more like 9 - 10 per US gallon. My overall average mileage for how I use the truck is 12.5 mpg.

[larry_barnhart]

When one of the above posts wins the race to the top what do they win??

chevman

[justme]

There is no easy answer, but if you pull a heavy load most of the time the lower gear is the better. Otherwise the high gear is prefer for light loads and intermittent heavy loads. Fuel mileage and engine wear (piston travel/mechanical stress) is important for long term wear and tear. For my experience the higher gears are preferred because I pull a heavy load intermittently. I pull a 165000GVW trailer with a F350 SRW with a 3.5 rear end. I have 40k miles on the trailer and 90K miles on the 2012 diesel truck. The TV pulls very well and if the tranny starts hunting between 5th an 6th gear, I lock it in 5th and everything is good. The torque on the F350 is fantastic and pulls grades very well. I see no need for 4:11 rear end.... I average 12mpg pulling 20mpg not pulling. I set the cruise control to 60 mph pulling and 75mph not pulling.

[4x4ord]

It is. He is losing more power than you in his transmission going through 5th gear to speed the driveshaft up and loosing additional power in the 4.10 rear end slowing the axle back down again.

[Me_Again]

4x4ord wrote:

Wild Card wrote:
Yall can throw all the numbers you want out. I can yank my 16k# hauler up a 10 mile 6% grade at 65/70 miles an hour like it's nothing with my 4.10s. 1/2 to 1 mile to the gallon is pointless in the equation. I will smoke ya at the stop light and at the top of the hill. Bragging rights. ..bragging rights

That is the point.... your Cummins can tow your 16k hauler up a 6% grade at 70 mph which means, you don't have the best gear ratio for your application. It obviously works but just not as good as 3.42 gears for such a light load. 4.10 gears are better suited for a heavier trailer and/or on steeper grades. If you're foot is to the floor and your doing 70 mph with 4.10 gears up that hill then your in 5th gear and running at 2335 engine rpm. With 3.42 gears you'd be in 4th gear running at 2530 rpm and accelerating.

Is my 1.0 to 1 direct drive 4th gear more efficient than his .77 overdrive 5th gear??? Chris

[4x4ord]

Wild Card wrote:
Yall can throw all the numbers you want out. I can yank my 16k# hauler up a 10 mile 6% grade at 65/70 miles an hour like it's nothing with my 4.10s. 1/2 to 1 mile to the gallon is pointless in the equation. I will smoke ya at the stop light and at the top of the hill. Bragging rights. ..bragging rights

That is the point.... your Cummins can tow your 16k hauler up a 6% grade at 70 mph which means, you don't have the best gear ratio for your application. It obviously works but just not as good as 3.42 gears for such a light load. 4.10 gears are better suited for a heavier trailer and/or on steeper grades. If you're foot is to the floor and your doing 70 mph with 4.10 gears up that hill then your in 5th gear and running at 2335 engine rpm. With 3.42 gears you'd be in 4th gear running at 2530 rpm and accelerating.

[Me_Again]

Wild Card wrote:
Yall can throw all the numbers you want out. I can yank my 16k# hauler up a 10 mile 6% grade at 65/70 miles an hour like it's nothing with my 4.10s. 1/2 to 1 mile to the gallon is pointless in the equation. I will smoke ya at the stop light and at the top of the hill. Bragging rights. ..bragging rights

OK, when do you want to meet at Davis Dam? I will bet we get to the top at about the same time. My combined weight is around 24,500, what is yours? Chris

[Wild_Card]

Yall can throw all the numbers you want out. I can yank my 16k# hauler up a 10 mile 6% grade at 65/70 miles an hour like it's nothing with my 4.10s. 1/2 to 1 mile to the gallon is pointless in the equation. I will smoke ya at the stop light and at the top of the hill. Bragging rights. ..bragging rights

[RCMAN46]

4x4ord wrote:

Pop-Pop C wrote:
You may sacrifice some mileage with the 4:10 as a daily driver but when on the road will be highly beneficial. There can be steep hills or mountains where ever you may go.wouldnt want to limit your self just to,flat lands. Not sure where that would be.

You'd have a hard time finding a circumstance when the 4.10 would be beneficial over 3.55 gears towing a 16,500 lb rv. It would take an 8% grade at 60 mph before the 6.7 would even start pulling down from 2600 rpm in 4th gear with the 3.55 final drive. The 4.10 is reserved for heavier loads where the engine hasn't enough power to manage 60 mph.

If we pick 60 mph as a desired speed both the 4.1 and 3.55 will require 3rd gear in the Ford for near 2600 rpm (max hp)

At 2600 rpm (max hp) the 3.55 will net 57 mph where as the 4.1 will limit the speed at 49 mph.

I would say the 3.55 is the better choice for the Ford 6.7.

[4x4ord]

Pop-Pop C wrote:
You may sacrifice some mileage with the 4:10 as a daily driver but when on the road will be highly beneficial. There can be steep hills or mountains where ever you may go.wouldnt want to limit your self just to,flat lands. Not sure where that would be.

You'd have a hard time finding a circumstance when the 4.10 would be beneficial over 3.55 gears towing a 16,500 lb rv. It would take an 8% grade at 60 mph before the 6.7 would even start pulling down from 2600 rpm in 4th gear with the 3.55 final drive. The 4.10 is reserved for heavier loads where the engine hasn't enough power to manage 60 mph.

[goducks10]

bluegrass smokers wrote:
The tire size is 245/75SR17.

So far what I am reading is the truck will work with either gear ratio since the weight is 16500? The 3.55 will make less RPMs when driving at highway speeds without the trailer load?

I am a wood/building guy, I know where the fuel goes in on my truck and that's about it.

You can put your numbers in here and see what your rpms would be.
http://www.crawlpedia.com/rpm_gear_calculator.htm

3.55's are def the way to go with those tires
5th @65=2140
6th @65=1698

4.10
5th @65=2473
6th @65=1961

[Pop-Pop_C]

You may sacrifice some mileage with the 4:10 as a daily driver but when on the road will be highly beneficial. There can be steep hills or mountains where ever you may go.wouldnt want to limit your self just to,flat lands. Not sure where that would be.