I may want to go with the max trailer tow package, not for towing, but for the increased payload. I assume it has a different axle and am wondering how that would affect mpg.

 

When I ordered max tow it did not change axle ratio. It is still 3.73
I also got the HD payload package. 8200lb on a supercab 4x2 with 8 foot box. I really don't think you need to change axle ratio with 420 poundfeet of torque starting at 2500 rpm.

Al

 

Max trailer tow REQUIRES the 3.73 axle. HD package also requires it, so if you already have it ,you can't add it.

To answer the OP. Rear axles for the trucks vary from 3.15 to 3.73 (not counting the 4.10 with the Raptor or FX4). We don't know which axles Ford used for EPA testing but would assume the highest 3.15 or 3.31. So with the 3.73 I would expect maybe 1 or 2 mpg lower but then again maybe not. The 3.73 will be better off of the line, so city mileage may actually be better because it will take you less gas to get moving. Hwy mileage will be a little lower.
If you commute over 100 miles a day you would want the 3.15 or 3.31 for max hwy mpg. Me, personally I went with 3.73 but will drive 65-70 instead of 75 to make up the difference. In other words, the 3.73 will run a slightly higher rpm than the the other axles, therefore burning slightly more fuel. By slowing down a few mph, you can run the same rpm and achieve the same mpg

 

Thanks. I was actually thinking in terms of the FX4, so I guess I need to knock off a total of 2-4 miles? On the other hand, the official report is that the 4wd Ecoboost is 15/21 mpg. If in fact the FX4 has a different axle, it makes me wonder whether it would not be better to get a nonFX4 4WD, assuming I am not going to do any hard core offroading (I do want to go off road, but plan to be sane about it). Thoughts?

 

The FX4 comes standard with the 3.73 elocker rear end. So you don't have to take the 4.10.

Your other option, if you want to go off road is to get an XLT or Lariat, or whatever trim you like, then add the off road package which has 3.73's as well. As far as I know the FX4 has a different interior, the 4.10 axle option and that's about it. As far as I know it has nothing else to make it handle off road better than any other F150 with the off road package. It does have tuned shocks but then so does the off road package for the other trim levels.

Personally, I am scared of the 4.10 due to potentially lower mpg (of course with the 6 speed tranny no one really know what mpg they will get). If I was going to be towing 10000 lbs every week then I would consider it.

I have a F150 XLT SCAB 4x4 with ecoboost, max tow, 3.73, off road package on order.
I hope to get 17-18 combo city/hwy and 20-21 on the highway. I have been reading reports of the guys running across the U.S. doing the ecoboost tours getting 24mpg, so I figure I should be able to get over 20 easily. Plus with the new way they calculate mpg, it is easier to obtain the EPA figures

 

I was looking at ordering the Ecoboost Supercrew 6.5 box FX4 package and selected max tow with 3.73's, however I did not see any GVWR options to select on the build and price at Fords site....I'm with JohnDeerefarmer on the 3.73's, I think it's the perfect combo and with a deep first gear in the 6 spd tranny it will move a load up to speed with ease and still get decent economy.

 

That is exactly right.

The new six speed has such wide ratios that there is no need to fear the 3.73 differential gear. At around 75 the engine is spinning about 2,000 rpm,

 

My GVWR for a SCAB 4x4 with 6.5' box and max tow is 7700 lbs. Payload is 2040 lbs.

For a SCREW 4x4 with 6.5 box and max tow, it is 7650 lbs with a payload cap. of 1970 lbs

Without max tow the GVWR drops 300-500 lbs

 

The only way you can get the Heavy Payload package is with an XL or XLT regular cab or super cab with 8 foot bed.

 

SCrew 4wd 6.5 GVWR is 7,700lbs
SCrew 4wd 5.5 GVWR is 7,650lbs.

Payload figures are maximum less options.

 

Anyone else think that the 3.73 or higher rear end isn't needed and goes against the purpose and thoughts behind ecoboost torque curve? Just like the new diesels....6 speed transmission and that awesome torque curve...even when towing I don't think it's needed. We are thinking pretty old school on rear ends here.

 

Depends on whether you want to tow something or you have a daily driver.

I personally don't want anything less than a 3.73 to prevent excessive down shifting while towing heavy.


Sure the ecoboost has a better torque curve and more of it than previous engines but there was no industry standard before for towing. Now it's gonna take the torque of the ecoboost as well as the 3.73 to meet the new SAE standards. I guarantee you that Ford doesn't want to say that the ecoboost can tow up to 11,300 lbs this year and then have to lower it when the standards take effect. Toyota has already lowered theirs. I see that as bad for business.

 

It might be bad for busines but Toyota's rating is real life. I wish all manufactures used the same system right now.

These half tons can't handle that weight and people shouldn't think they can do it.

If you tow that much weight that often you should be doing it with an F250.

 

My thoughts on this are that engine speed [RPM] is not the sole defining factor in how many miles per gallon a vehicle gets.

To me, mileage is a product of engine efficiency.

Gearing is only but one factor in efficiency, because it has a direct effect on engine load which, in turn, has an effect on things like intake manifold vacuum and fuel injector duration. An engine that has a large load on it will produce a lot of vacuum and will burn a lot of fuel because the injectors will be "open" for a longer duration and be spraying fuel at a very high rate. This is true regardless of the engine speed.

I can observe this phenomenon regularly with my F250 which has a manual transmission. Even in low engine speed situation, my baby 5.4L truck will use a whopping 12 gallons of fuel per hour (!) with a high engine load. One way I can replicate this is by putting the transmission in 6th at 35mph and flooring it. My engine is only turning about 1500RPM but those injectors are flowing some fuel!

By this logic, it would be more fuel efficient for me to drive in 2nd gear at 35mph with the engine turning 5000RPM because then the engine only needs 8 gallons per hour.

However, if I accelerate normally using 3rd or 4th gear at 3000RPM I can accelerate prudently and use 5.5 gallons per hour during such a maneuver.




I guess what I'm trying to say is that not everything is dependent on the engine RPM. A 4.10:1 ring and pinion ratio will not guarantee worse mileage than a 3.73:1 ratio. Depending on your use, the numerically higher axle ratios could turn better mileage numbers because they reduce engine load through multiplied gearing. You have to ask yourself what kinds of loads do you normally expose your engine to: high payload, trailer towing, larger tires, frequent starts and stops?

You have to keep the engine in it's powerband and, luckily, the new EcoBoost 3.5L has a huge, broad powerband. A jump from 3.73:1 to 4.10:1 usually represents about a 200RPM jump in engine speed on a modern overdrive transmission. This is nothing to an engine that holds it's peak torque for a solid 3000RPM range. I could be wrong, but the increased gearing should only further reduce engine loads and, perhaps... hopefully... actually help mileage in a truck application.

These are my 2.5 cents
LoL
Flame Away

 

The EB tow ratings falls off when you go with a lower rear end (#).

I wouldn't want to be geared too high.