4:10 or 3:73 ?

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.

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.

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

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.

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.

bluegrass smokers wrote:
OK someone help me out here and let me know if this is the correct line of thinking. With a 4.10 I can tow easier but driving unloaded the truck will work harder at high speeds and with the 3.55 it works harder towing but easier at unloaded highway speeds? Basically right? My fifth wheel is about 16500lbs.

I am looking at 2 2017 Ford DRW F350s. Both trucks are close on equipment but the rear ends are different. I am trying to figure this out. And the truck will have to be my daily driver along with family trips without the fifth wheel.

The 2017 DRW with 3.55 gears is rated to handle a 27,000 lb trailer. You don't need to consider 4.10 gears for a 16,500 lb trailer. Even the 2017 SRW is rated for an 18,000 lb rv with 3.55 gears.

The weight of the trailer, the wind resistance and incline of the road determine how much power is required to tow your trailer. The gear ratios just allow the engine to run at a suitable rpm. If your towing a 16,500 rv down a level highway you only need to be making about 100 hp. The 6.7 can produce 925 lbft of torque at 1600 rpm. That means it is capable of making 282 HP at 1600 rpm. This engine can very easily handle a 16500 lb trailer. Your tire size and speed dictate the rpm of your rear axle...so a 2017 Ford dually at 60 mph will have its rear axle turning 640 rpm. With a 3.55 axle ratio the transmission can select any of any of 4 different gears to obtain that rear axle speed:

3rd gear - the engine will be turning 3453 rpm .... it might select 3rd gear for grade braking going down a steep hill.

4th gear - the engine will be turning 2613 rpm ... it will select this gear for pulling up a steep hill where maximum power can be obtained. This is a good gear to be in when the engine is working hard as there is the least amount of power lost in the drive line while running in 4th gear. (the ratio which is closest to 1:1)

5th gear - the engine will be turning at 1954 rpm....the transmission will select this gear in a high wind situation or when pulling up a moderate hill.

6th gear - the engine will be turning 1522 rpm ... this gear will be selected while cruising down the highway, pulling in light winds or slight inclines.

Which size tires are on the truck you're looking at? That will make a difference in what RPM's you'll see.

Wow, 7 pages of discussion about ratios. Guess I will just keep my '04.5 5.9L 325 HP 600# torque,3.73 ratio truck with 210K and counting. I tow 19-20K combined at 65 MPH and 1800 RPM on the interstates or two lane roads where allowed at 10-11 MPG. I mostly tow from Indiana to east of the Rockies, west central Montana. Current trip has taken us from Montana thru the Black Hills into Colorado and on into eastern N.M. I have towed from Utah on I-70 to Indianapolis with this set up and not worried. Current trip will take us across TX, Ok, to Tn., to southern ILL, to Indiana on US-50 to home. Oh, the best part about the truck is it has been payed for for years. Good day ye all.

bluegrass smokers wrote:
OK someone help me out here and let me know if this is the correct line of thinking. With a 4.10 I can tow easier but driving unloaded the truck will work harder at high speeds and with the 3.55 it works harder towing but easier at unloaded highway speeds? Basically right? My fifth wheel is about 16500lbs.

I am looking at 2 2017 Ford DRW F350s. Both trucks are close on equipment but the rear ends are different. I am trying to figure this out. And the truck will have to be my daily driver along with family trips without the fifth wheel.

If we use the Cummins with the Aisin transmission when going about 60 mph.

Rpm with 3.42 in 5th gear 1712
Rpm with 4.1 in 6th gear 1680

If anything the Ram will do better with the 3.42

16500lbs will be nothing with all three of the current diesel pick-ups with any of the available rear gears.

OK someone help me out here and let me know if this is the correct line of thinking. With a 4.10 I can tow easier but driving unloaded the truck will work harder at high speeds and with the 3.55 it works harder towing but easier at unloaded highway speeds? Basically right? My fifth wheel is about 16500lbs.

I am looking at 2 2017 Ford DRW F350s. Both trucks are close on equipment but the rear ends are different. I am trying to figure this out. And the truck will have to be my daily driver along with family trips without the fifth wheel.