Geo4

We're getting ready to buy a new pickup, and found a little confusing information in regards to towing ratings. I looked through the towing forum, but didn't see this question asked before.

The towing capacity chart for the 2012 F150, 145" WB SuperCrew 5.0L V8, as having the same towing capacity (8000#) with either the 3.31 or 3.55 rear axle. I've found a few charts that don't even show the 3.31 as an option, and I know that's not accurate.

Does anyone have any other information on these two axles? And if they are the same, what's the benefit of buying the 3.55, other than worse gas mileage. (Gas mileage figures comparing the two would also be helpful.)

I want to avoid the 3.73 because I'm sure the mileage will be much less than either of the others.

We're currently towing a pop-up camper with our minivan (max 3000 trailer weight, and towing capacity of our van). The loaded weight of the camper is about 2600 lbs, but we're considering an upgrade to a proper travel trailer, which would be in the 6-8K range. I'm not completely sold on the need to upgrade to the EcoBoost yet, but I want to be sure of how the V8 options will perform.

Thanks for any help with this.

brulaz

The higher the rear axle ratio, the higher the rpm the engine runs at a given speed. So yes, the mpg is a bit worse when unloaded, but you also have a bit more HP and torque which is what you will want when towing a 6-8K trailer.

If you don't have the power, your tranny will have to downshift earlier on hills to boost the engine's rpm that way to get the needed power. So your mpg when towing could be the same (or worse) with a lower ratio rear end.

Also if you only tow on the flats, and have a high torque engine like the Ecoboost, maybe a lower ratio is fine. Or maybe the 5L V8 with a lighter trailer.

But one of the reasons I went for a 3.73 and an Ecoboost with lots of low-end torque was to avoid all that downshifting that my previous truck was doing. It was noisy and irritating. And we tow a lot and not just on the flats.

If you use the truck for just occasional towing then then you could get away with a lower rear ratio and let the tranny down shift more. Especially as the new Ford's with the 6spd tranny with tow/haul are much quieter than my old truck. I don't think you'd save gas while towing, but you would when not.

The difference in mileage is not huge between the gear sets, a few percent maybe. I think your choice of tires (All Terrain or Highway All Season) and wheel size (increased weight) will have a bigger effect.


If you're thinking of getting an 8K trailer, that's close to the limit Ford recommends for the 5L V8 in your config. The Ecoboost would be better.

Also, typically people add 1000# of gear/food/water to a a trailer's dry weight. I do anyway. So if you got a 6000# dry weight trailer instead of the 8000#, and added 1000# of gear, the 5L V8 should be ok (7000# total). But I would get the 3.73 rear end unless you only tow on the flats or only rarely. If you went with 8000+1000#, I would do the Ecoboost + 3.73.

And don't forget the truck's payload. An 8K trailer can have a tongue weight of 800-1200#, and a fifth wheel can have an even higher pin weight. The rated payload in the brochures does not include options, so you'll have to subtract those yourself.

Another reason I sold my old truck was that I was always exceeding the payload and GVWR by a few hundred pounds.

Hope this helps. But a lot depends upon what you'll be towing, where and how often.

papa tiger

The 5L is a great option, put the 3.73 in it if you plan to long mile trailer tow, no matter the GVW. Even with the 3.5L EB. Get the 3.73 to help with the condensation along with the hard pulls. Good gears make a great truck while low gear ratio axles make nice cars. With the 3.73 you have some tire size leaway in the future. Going up to 33" will reduce your gears down to 3.55 or so if you want to go that way then.

curtw48

I don't think you will see an appreciable difference in mileage with a lower gear set, and it will help you when towing. I have a 2009 Screw Lariat with 5.4L engine and 3.73 gearing, and my in dash computer is showing 19.2 MPG right now for my last tankfull on my daily 30 mile commute to work

smokeywren

brulaz did a good job with his reply, so I'll just embelish what he said.

With 5.0L engine, 3.31 is standard on a 4x2 and 3.55 is standard on a 4x4. 3.31 not available on a 4x4 with the 5.0L engine.

3.55 is optional is optional on 4x2 SuperCrews with 5.0L engine for those that want a bit more towing power. But the difference is not enough to change the GCWR or tow ratings. 7.25% difference, so at 1,700 RPM with the 3.31 you will be making 1,823 RPM with the 3.55 gears.

And with 3.31 or 3.55 gears, the HD payload pkg or max tow pkg are not available, so hitch weight and not gross trailer weight is the limiter. With a maxed-out SuperCrew 4x2, hitch weight will be the limiter with the 3.31 gears, and the 3.55 has the same payload capacity so it can't haul any more hitch weight than the 3.31. So the GCWR and "tow rating" is the same for both ratios, even though the 3.55 has more pulling power.

They are not the same, but the difference is only 7.25%. It's academic if you want a 4x4, because 3.31 is not available. The difference in a 4x2 is that the 3.55 gives a bit more towing power because of the higher engine RPM at the same road speed when climbing mountain passes or hills or coming up out of a river valley, such as on I-40 near Albuquerque or the steep grade between Bullhead City and Kingman AZ.

This only applies to 4x2 SuperCrews where 3.31 is std and 3.55 is optional. Your right foot will have a much greater impact on MPG than the 7.25% difference in gearing. When towing, the 3.55 should result in slightly better MPG than the longer legs of the 3.31. When unloaded, the longer legs should result in a barely measurable increase on MPG.

[quote[I want to avoid the 3.73 because I'm sure the mileage will be much less than either of the others. [/quote]

That was my thoughts, but I was wrong. I have the 3.15 ratio (4x2 EcoBoost) and I get about the same MPG as those with the 3.73 axle ratio. Only if you poke along blocking traffic will you get great MPG. But cruising with traffic at over 70 MPH and the rear end ratio doesn't seem to matter much - unless you go with a lot shorter legs than the 3.73 ratio.

An F-150 without the max tow pkg or HD payload pkg will be overloaded over the GVWR of the pickup with the 3.31 or 3.55 ratio and a TT that weighs 6,000 pounds or more. My F-150 is overloaded over the GVWR of the pickup with my TT that weighs only 5,000 pounds. So you need at least the max tow pkg with EcoBoost engine or HD payload pkg with the 5.0L engine, and that requires the 3.73 ratio. 3.73 with e-locker diff gets you the max tow pkg with 500 pounds extra payload capacity (for hitch weight) if you have the EcoBoost engine. HD payload pkg gets you 1,000 pounds extra payload if you have the 5.0L engine and 3.73 limited slip axle. And with the EcoBoost engine with 3.73 LS axle, you get both max tow and HD payload packages.

Also note the tow ratings. 5.0L engine with 3.55 gears in a SuperCrew 4x4 with 6.5' bed has a tow rating of 7,500 pounds. That's inflated by about 1,000 pounds, so the max trailer weight I'd want to tow is round 6,500 pounds.

5.0L engine with 3.73 gears in a SuperCrew 4x4 with 6.5' bed and HD payload pkg has a tow rating of 9,200 pounds. So a realistic max trailer weight of about 8,200 pounds. That gives you a much broader choice in TTs.

But the EcoBoost engine is the choice for dragging a TT. Order the 3.73 limited slip axle and you get both the max tow pkg and the HD payload pkg. Tow rating is over 11,000 pounds, so that means you can tow a TT that weighs up to around 10,000 pounds without being overloaded. The EcoBoost engine in SuperCrew 4x4 with max tow pkg will pull an 8,000 pound TT with no sweat, even up out of Death Valley in August.

RedOne

I have been driving mine all over the Widwest this summer with temps regularly over 100 deg and have had no water or tranny or AC temperature problems. Granded we don't have the hills of out West but we do have the Ozarks with 500 to 1000' elevation changes on a regular basis. My truck pulls these hills and roads around here with no problem what so ever. Stopping or slowing the rig down is very good also. Get it set up right and there will be NO white knuckle driving at all plus you will not be worn out by the time you get to your destination. The rig I have is the easiest trailer setup I have driven in over 35 years.

isthatahemi

Just a note on gear ratios. With the 6 speed, if you are running taller gears, it is likely that it will just select the next lower gear, possibly yielding a higher towing RPM. It is not as simple as "a higher gear= more RPM at a given speed". Unless you are towing in 6th gear, that is just not true. Unfortunately, sometimes you will find a more optimal combination with a taller rear axle gear.

Example - A friend of mine tows a trailer with an older truck with a 4 speed, he found that his trailer was too heavy for his previous truck with 3.73's in overdrive, so he ordered a new truck with 3.30's, and towed in 3rd. He got better mileage all the time, and his truck towed better, as it was no longer over-revving in 3rd. Alternatively, he could have gotten 4:10's right? His truck would have accelerated better and more efficiently as well, when towing.
My example is that my 3.7 just barely holds 5th, 2500rpm@ 68mph. Otherwise it is in 4th gear, around 3200rpm. With 3.53's it would comfortably tow in 4th, at slightly under 3000 rpms. It just so happens that 5th gear is questionable.

Also, shorter gearing will typically yield better mileage at lower speeds and stop and go. So if you do a lot of that, keep it in mind.

Oh yeah, if you like effortless towing, get the ECO! Good luck!

jml79

I have the 5.0 with 3.73's and tow 7-8K horse trailer loaded. I find it more comfortable to lock out 6th and run in fifth most of the time if I am below 60 mph and only allow 6th when I am running at 65. The truck just bogs down in 6th below highway speeds and ends up downshifting at the slightest grade. I get amazing gas mileage with my truck compared to my 08 Jeep with a hemi. I would go for the extra capacity and not worry about the few cents difference in fuel. Plus the 3.73 allows for a lot more trim levels than the taller axles like FX4 and Lariat with Max Load.

brulaz

You're right and that's an interesting example. It's the final drive train gear ratio (and tire size) that counts. And a 6 spd tranny makes finding that RPM sweet spot all the easier.

One thing though, if your friend didn't tow that much, the 3.30 and driving in third when towing makes a lot of sense, because he'd have better mpg when he was Not towing, compared to a 4.1 and driving in fourth. However, if his truck was basically a tow-truck, like mine, the 4.1 would make more sense, like you say.

I suspect that smokeywren, with his 3.15 rear end, only occasionally tows and was looking to maximize the mpg of his daily driver (?). That's an unusually low rear end ratio and is only available with the Ecoboost's low-end torque .

papa tiger

The 6 speed complete changes the towing ball game with a HD tow package.