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?

[Bedlam]

OD = OverDrive
DOD = Dual/Double OverDrive

[GoPackGo]

blt2ski wrote:
One needs to remember, torque is not always what your want. HP is also needed. At the end of the day, even back 20 years ago, one geared a rig so you had the HP needed in high gear to move a rig. That is why in navistar runs at 2500 at 60 mph, as that is where it produces the hp to move 26K lb, around 150hp. Then again, my motor produces a peak 175/335 hp/torque. A 3.73 gear set would be nicer, but i could not run at 55-60 in high gear, which for me is direct.

Gearing in trans can make up a lot for what is in the pumkins.

I'm also not one for running lower rpms in dod, it take hp to turn a OD and DOD trans. Two setups turning 1800 rpm, the one with 4.56 gears running in dod will be potentially using more fuel than a rig in direct with say 3.08 gears. BUT, to get the load going, the 4.56 setup may need a 6-1 first gear, the 3.08 a 10-1 first gear. At the end of the day, it is being in the correct final ratio for how you tow, pull etc, than it is what gear ratio is in the pumkin. You need what is in both the pumkin and trans to know what will be correct for YOU!
i would take the lowest set. Then again, i only drive up to 55-60 mph for the ost part, as it is not legal to drive 70 mph locally, so the lower gears give me a better rpm at 60 than the taller ones in DOD!

Marty

What in the world do you mean when you say 'DOD' ? Let me restate that - I worked for DOD for 30 years and we never once referenced our parent organization and gear ratios in the same sentence. Help me understand what you are stating !

[transamz9]

I pull 20,000 (28,000 combined) with 3.42's and have no problems taking off from a start on hills or pulling down the road.

[dwayneb236]

I have a Ford F350 DRW with the 6.7 and 3.73 and tow a 14000 lb. fiver. Pulls it with ease. Will be going to California with it next month and will really see how it pulls.

[Ford_Man]

3:73 works great for me towing a 13000 lb Montana with a 6.7 PSD. Had that combo in a 2011 and 2014 as well as the 2016 that I have ordered now.

[mkirsch]

Old conventional thinking is that you need a 4.10 or lower ratio if you want to pull something, but that is from the days when 1:1 was the highest ratio you could get in a transmission.

Some people just haven't gotten out of the '70's.

These 6+ speed transmissions with the stump-pulling low 1st gear ratio, and no real "direct" gear (i.e. 4th is 1.15:1 and 5th is .87:1) have completely changed the game for towing and hauling.

[blt2ski]

One needs to remember, torque is not always what your want. HP is also needed. At the end of the day, even back 20 years ago, one geared a rig so you had the HP needed in high gear to move a rig. That is why in navistar runs at 2500 at 60 mph, as that is where it produces the hp to move 26K lb, around 150hp. Then again, my motor produces a peak 175/335 hp/torque. A 3.73 gear set would be nicer, but i could not run at 55-60 in high gear, which for me is direct.

Gearing in trans can make up a lot for what is in the pumkins.

I'm also not one for running lower rpms in dod, it take hp to turn a OD and DOD trans. Two setups turning 1800 rpm, the one with 4.56 gears running in dod will be potentially using more fuel than a rig in direct with say 3.08 gears. BUT, to get the load going, the 4.56 setup may need a 6-1 first gear, the 3.08 a 10-1 first gear. At the end of the day, it is being in the correct final ratio for how you tow, pull etc, than it is what gear ratio is in the pumkin. You need what is in both the pumkin and trans to know what will be correct for YOU!
i would take the lowest set. Then again, i only drive up to 55-60 mph for the ost part, as it is not legal to drive 70 mph locally, so the lower gears give me a better rpm at 60 than the taller ones in DOD!

Marty

[4x4ord]

Overloading a truck (to the degree I do) is not wise. Duals for heavier trailers have something to offer. But gear ratios are different. A higher numeric gear ratio is a disadvantage when it is not needed. It will still do the job just not as efficiently as the truck with the right gears.

[1jeep]

And that's where we don't agree, I spent last season at my trucks limits and didn't like it when I did tow. I would rather be comfortable when I do need it rather than overload my truck.

[4x4ord]

1jeep wrote:
Luckily for me I have more faith in fords engineering skills and trust that they may have thought about these things when trying to pull the highest tow rating from their 1 ton trucks.

Exactly. The srw trucks are designed for towing small RVs upto about 16000 lbs and have 3.31 and 3.55 rear ends. It's not till you're towing over something like 24,000 lbs that they put you into the 4.30 ratio. And even at that weight a person may or may not be happier with 4.30 gears than 3.73.....it depends on the road surfaces and hills. Rv'ers typically run on nice smooth hard surfaces and some use their truck running empty more than towing. For instance even though I tow 30,000 lb trailers with my srw I would rather size my truck for running empty (and towing my little RV) and make due with what I have for the times I tow real heavy.

[1jeep]

Luckily for me I have more faith in fords engineering skills and trust that they may have thought about these things when trying to pull the highest tow rating from their 1 ton trucks.

[4x4ord]

Prior to the days of computers a diesel engine was always able to obtain it's greatest efficiency at the RPM where it produced its highest torque value. Today I don't believe that is necessarily true. As a general rule, though, gearing up and throttling down conserves fuel. So running 1700 rpm is great when you need less than 260 HP. So running in 6th at 1400-1700 is ideal for light loads. So again the low power demands go through the overdrive gears.

[Bedlam]

I'm not sure I can agree with this thinking. It would mean I should get 3.55's and just run the transmission in 4th gear or 3.31's and run in 3rd the way you are describing it?

Higher ratio final drives also put the gear ratios closer together so the transition between shifts is less severe. I have always chosen my top cruising speed and geared appropriately for my typical load to prevent transmission hunting. This is typically close to where you develop maximum torque. I run 1700 RPM somewhere around 55-60 mph which is just fine for my CTD. The PSD develops torque at 1600 RPM, so you can do the same math to find the ideal final ratio.

[4x4ord]

If you hook a heavier trailer onto that truck with the 3.73 gears and you are regularly pulling loads where the engine doesn't have the power to maintain 50 - 60 mph than it is time to think about 4.30 gears. For instance at 2650 engine rpm with 4.30 gears the truck will be traveling about 50 mph in 4th gear. The 3.73 truck would choose between 3rd gear running at 3030 rpm or 4th gear running at 2300, neither is as ideal.