2talltechie

I am having trouble pulling the trigger on a 4x2 Lariet because I can't pick an axle. I plan to pull a travel trailer someday, so tow capability is important. Most everyone automatically goes for the max tow package and the 3.55 axle. However, if you believe in the J2807 standards, the 3.15 axle pulls 10,700 lbs. with the 3.5L EB and it certainly will deliver better highway mpg. This is more than last years model with the 3.55 gear, and about the same as this year's V8 with the 3.73 axle. Again, j2807 rating, not Ford's.

This was posted on the forum in 2011. Still seems relevant today.

Why do I need the 3.55 axle if my future travel trailer is at least 1000-2000 lbs. under 10,700 lbs? Payload will be an issue long before the tow weight cap is reached. This year Ford dropped down a gear on the max tow package to reflect the capabilities of the EB and its overall weight loss. I don't need to pull 11,900 lbs.

DieselDawg

If you plan on pulling that much weight...I would go for the lower gears. My thinking is that with pulling, I would be putting e-rated tires in place of the stock passenger tires...and they would probably be a bit taller...further lowering your effective gear ratio. 13% diff could be a big deal IMO.
While pulling, at some specific weight, with a taller 3.15s you might actually end up in 4th or 5th gear...while with 3.55 (or 3.73s like I have) you might spend more time in 5th or 6th. Just food for thought.

brulaz

I pull 8000# with a 3.73 axle at around 60mph. And I'm usually in 6th, dropping to 5th on moderate slopes, and down to 4th on steeper climbs on the Interstates.

I'm sure you can pull 9000# with a 3.15 axle. It's just that you will be in 5th and 4th most of the time. Occasionally going to 3rd on steep slopes. I can't imagine you being in 6th gear much at all. And if you pull fast, with increased air resistance, you may spend more time in 4th. I know I spend more time in 5th with strong headwinds

You end up losing a gear (6th) and have more of an rpm jump between gears as you get lower. That could be distracting I suppose. Sort of like going back to an older 5-speed tranny when towing.

But for me, the 3.55 gear would be better. But we tow more than 50% of the time and the truck is not a "daily driver".

acadianbob

Lariats have been known to have lower payload capacities. You might want to make sure of your payload as well to make sure you have enough to handle tongue weight and cargo load.

jkenprice1

I've been thinking about changing from 3.55 to 4.10. I pull a 14 enclosed trailer for work. Most of my drivivng is in town, so my biggest concern is being about to keep up with stop and go traffic. I googled f150 4.10 and found several post by guys who actually had 4.10's. Several said they got better mileage with the 4.10's, and had more fun drivivng wen not towing. To each their own, but I'm planning on switching to 4.10's with a Detroit Trutrac diff

2talltechie

Ok, then tell me this. Would you think the same gear issue would apply to a V8 4x4 with the max 3.73 gear ratio? The J2807 specs say they that my proposed 3.15 EB is within 200 lbs in towing capacity. How could they come up with the same rating unless both performed equally?

I'm thinking that the J2807 standards should be giving some great insight to towing community, but the specs never seem to get mentioned in the forums. No big deal to the truck community?

DieselDawg

Tow Ratings alone do not dictate how well a vehicle will tow...only what it is rated to pull. Nearly 100% of the time, lower gears tow better and taller gears (also nearly 100% of the time) will get better mileage when not towing. If you are buying a truck and wanting to use it as a truck...gearing is at the top of the list for concern. When I purchased my 2012 EB 4x4 with 3.73's, I was looking ahead. I figured I would give it a lift with taller tires...and was planning on getting a Travel Trailer down the road. Worked out for me. Now just figure what works out for you.

brulaz

Will the V8 with 3.73 gearing and pulling a 9000# TT spend most of its time in 5th gear? Think so. It needs the higher rpms to get the power. And the engine is designed to run at those higher rpms all day long. Pretty sure a lot of 5L owners lock out 6th gear when towing, especially when towing a 9000# TT.

The J2807 deals with over heating and braking issues, and whether the truck can maintain speed towing up a slope and so on. It doesn't concern itself with which tranny gear the truck is in when towing.

It sounds like under the J2807 testing conditions, the 5L with 3.73 and the EcoB with 3.15 are putting down about the same amount of power at the same testing speed with the same load going uphill. The EcoB with 3.55 can do a bit more (power and load) at the same testing speed going uphill.

daveak

My travel trailer is around 7500# fully loaded. I spend most of my time in 6th gear on the freeway (5.0, 3.73) And have a mpg towing average of 11.1. Happy with that I am. Overall, my combined mileage is 16.7 (without towing) with about half on the hwy. I can get 20, but I have to be pretty careful on the throttle..... I don't get 20 on the hwy very often.

I got the 3.73 with the 5.0 because I knew I would be towing and I am very happy with it. If going with the EB, you should be fine with a 3.55 - any lower and you will find yourself out of 6th gear more often when towing and engaging the turbos more and losing mpgs. Your choice.

The more often you tow, the better gearing you want. You know your driving style better than any of us, pick a combo that works best for you.

jkenprice1

There are really 2 issues. How much your truck is rated for and how well it performs. Lower gears (3.73-4.10) will usually perform better than higher gears ( 3.31-3.55). Alot of people say lower gears get worse mileage. Theoretically that may be true, but in real world driving it's not. It has to do with torge multiplication. Going 60 mph with 3.31 gears may result in the engine running at lower rpms than a truck with 3.73 gears, but the torque multiplication of the lower gears means it can actually take less energy to more the vehicle down the road. There re more factors nvolved than just rpm's

The other thing you need to reallize is Ford plays with the numbers when determining the load and tow ratings. That's why you see so much difference from year to year and from model to model. For example, a lot of people believe the 5.0 can actually tow/haul more than they are rated for, but Ford lowers the numbers on the 5.0 to get people to spend more for the 3.7.

Whichever way you go, the other thing you need to realize is, you can only legally tow/haul the weights that are listed on you door sticker. If you bought a 3.7 with the 3.31 and found it didn't do what you wanted it to, you could change diff ratio's and practically and safely tow more, but your still limitd tow what the sticker says. If you have any double about how much you want to tow, make sure you get the configuration that can meet you needs.