Gear ratio advice 3:73 or 4:30 on Super Duty

[austinjenna]

I am in the beginning stages of looking for a new TV and was looking at the Fords to start off with. (Dont worry Dodge fans I will look at them next) I see that Ford has either the 3:73 or 4:30 gears for what I would be interested in, 4wd, dually, crew cab. Currently my fiver is only 11k but all the new ones we look at are in the 16K range so I am looking to future proof myself a bit. My truck is also my daily driver.

My question is what gears would you recommend. Will I notice any big changes in MPG? We are currently weekend campers with one/two longer trips a year, but in the next 5-6 yeas that might change to more longer trips.

There is a 3K towing difference between the 2 gears but honestly if I am getting something that weighs 26k I will probably get a MDT.

Any advice?

[4x4ord]

The point is that running power through gears produces heat. The less you speed up and slow down shafts the more efficient you are at getting that power to the pavement. This is why the engineers have designed overdrive gears into transmissions. The idea is that when high power is required the transmission will drop out of the overdrive gears to increase the engine rpm and run the power through gears closer to direct. So when high power is required it is better to be running in 4th gear at 2770 rpm and 60 mph with 3.73 rear gears than to be running 60 mph in 5th gear with 4.30 gears at 2387 engine rpm. For one thing the engine can produce more power at 2770 rpm than it can at 2387 and secondly the prpeller shaft is not being uneccessarily sped up just to be slowed back down by the rear end. I'm not saying that your set up is not going to work but I am saying that for lighter trailers such as all but the very heaviest of RV's 3.73 gears are a better choice than 4.30 gears with the new powerful diesels.

[1jeep]

If you really believe that minimal difference between 3:73 and 4:30is going to wear out the rear before I replace this truck then I think your dreaming.

Why would I bypass the tranny cooler, that would affect the truck no matter what gearing.

[4x4ord]

1jeep wrote:
Wow...all the expert opinions yet only a few of us with real world experience.

I have a 2016 f350 drw diesel with 4.30 gears, as I posted earlier but I was slightly wrong on the engine rpms, at 70mph the truck turns 2200rpms. I have yet to experience such heat or struggle that some think I would.

Also as I noted earlier I have the heavy tow package wihich gives it the wide track front axle as used in the f450. And it has tighter turning radius than my previous f250 crew long bed, both truck s are the same length.

I have zero regrets buying this truck as it is configured, just wish I did it last year when I bought my 5th wheel.

If you don't think your producing any heat try bypassing the transmission cooler and see how far you go. I did point out that the advantage of a tighter turning radius might offset the advantage of having the right gears for some individuals.

[1jeep]

Wow...all the expert opinions yet only a few of us with real world experience.

I have a 2016 f350 drw diesel with 4.30 gears, as I posted earlier but I was slightly wrong on the engine rpms, at 70mph the truck turns 2200rpms. I have yet to experience such heat or struggle that some think I would.

Also as I noted earlier I have the heavy tow package wihich gives it the wide track front axle as used in the f450. And it has tighter turning radius than my previous f250 crew long bed, both truck s are the same length.

I have zero regrets buying this truck as it is configured, just wish I did it last year when I bought my 5th wheel.

[4x4ord]

What people are failing to understand is that you create heat....loose power when you transmit power through gears. If you want your engine tuning at say 2200 rpm you can run in fifth gear with a 3.73 rear end or sixth gear with a 4.30 and either way your traveling almost the identical speed. The 4.30 set up is speeding the drive way up in the transmission and then slowing it way down in the rear end so it will loose more power to heat and put less power to the pavement. Additionally the 4.30 set up looses the benefit that the 3.73 has of being able to shift up and drop the RPM down to 1700 when the load is very light. Unless your regularly pulling 30,000 lbs or running in very steep hills or off road where highway speeds are not attainable you don't want 4.30 gears for an RV. If you think the advantage of having a tighter turning radius out weighs having the right gears then do what you want. Does the f350 with 4.30 gears even come with the wide track front axle?

[Hannibal]

After owning and towing with everything from 3.07 to 4.56, I prefer the 3.73 gas or diesel. Even with my lethargic 310hp 5.4L, the 3.73 matches the power band of the engine at 60-70mph better than the other ratios.

[1jeep]

travlingman...its amazing how much better this truck turns with the wide front axle, that option you wont regret!

[Travlingman]

Mine has the 3.73, no problems pulling 15.5K through the mountains. Next truck will have the 4.30. I want the wide track front end.

[1jeep]

mkirsch wrote:
+1 on the 3.73.

The engine will be wound out at 65MPH with the 4.30 gears, but it will go straight up the mountain, pulling a mountain, in 6th gear.

Not true, 65mph its turning about 2200rpm.

[4x4ord]

mkirsch wrote:
+1 on the 3.73.

The engine will be wound out at 65MPH with the 4.30 gears, but it will go straight up the mountain, pulling a mountain, in 6th gear.

You don't want it to be pulling hard in 6th gear. That is why the top two gears are overdrive.....when the axle ratio is sized right for the work the truck is doing the transmission will downshift to 4th gear and the engine will rev to where it makes its power. So when the truck is using its power you want the power running straight through the transmission (4th gear) so there is less parasitic power loss. Overdrive gears are for cruising. If your truck is pulling 6% grades in 6th gear you've got the wrong truck for your RV unless you're pulling 14% grades the rest of the time.

[mkirsch]

+1 on the 3.73.

The engine will be wound out at 65MPH with the 4.30 gears, but it will go straight up the mountain, pulling a mountain, in 6th gear.

[Garry_Gayle]

I have a 2015 F350 4X4 DRW 6.7 with the 3:73 gears pulling a 38' Mobile Suites that weighs 18K, I have towed all around the west in the mountains and I am happy with my choice. I get around 9-10mpg towing and 17mpg cruising at 70 mph.

[4x4ord]

The srw is offered in 3.31 and 3.55. The dually in 3.73 and 4.30. I pull very heavy trailers in sometimes very soft ground with my 3.55 ratio. (I sometimes pull over 30,000 lbs with my truck). I put just under 100000 miles on my 2011 and had zero issues with it. These new trucks are capable of putting 23000 lb ft of torque on the rear axle in low gear with a 3.55 ratio rear end. I hardley notice a trailer behind me starting out with the 3.55 axle. Don't even think about putting a 4.30 in your truck. If want more torque on your axle to back a trailer onto some blocks or pull it though mud or soft ground you can always shift to 4 low. In 4 low you can stick a 6" block behind your trailer wheel and the truck will push a 16,000 lb trailer up on the block by shifting the transmission into R and removing your foot from the brake. I wish I could have gotten a 3.31 ratio in my new Platinum but that ratio is not offered with 20" wheels. (Which all Platinum srw trucks come with)

[1jeep]

I have a 2016 f350 dually 6.7 with the heavy tow and 4:30 gears. the only other choice in dually is 3:73, while im sure it would be a little better on fuel I am getting 15.6mpg empty on the highway at 68mph.
My previous 2011 f250 with the 6.7 and 3:55 was getting just over 17mpg on the last tank, truck had 108k miles.

The way my truck came it is rated to tow 26k lbs, I believe the 3:73 was rated for 23k lbs.

Btw...this truck is my daily driver and I have no regrets with the gearing, I may pay a few more dollars at the pump but has had zero hesitation towing. Also I bought this truck because it was on the lot, if I were to order one it would have the 3:73 gearing just because my 15k lb trailer doesn't need what I have.

[GoPackGo]

I full time and have a 2013 F350 6.7, crew cab, Long bed, 4x4 dually pulling a 14k fiver. It has the 3.73 gears. For my rig I would not consider the 4.30 gears. It pulls great, been all over Colorado, Wyoming, Montana and Idaho as well as the California Sierras and it just pulls and pulls. Love this engine. And I would not want a daily driver with 4.30 gears. I tow about 8000 miles/year and another 6-7000 non-towing.

I usually tow at 58-60 MPH which equates to peak torque of 1650-1700 RPM. I normally get 11.5-12 mpg towing and every once in a while I get over 12. The fact that it is a 4x4 and a dually negatively affects mpg. And those big mirrors ! I keep thinking I should fold them in for a full day of towing just to see how much they affect things.

MPG is affected more by speed (wind resistance)then anything else - no matter which gear set you have. You are pulling a 13 ft tall brick at 60 mph - Wind resistance is the big factor here.