My last full size truck was a 2000 F-150 with the 5.4 V8 rated at 260hp and 350 ft/lbs. The truck came with the 3.55 rear end.

Overall performance was just fine with regard to pulling power but I would have preferred a 3.91 rear end if that was available. That would make freeway cruising a gas burning operation so a taller fifth gear would have been necessary.

Well now it is 2011 and I am strongly considering a new 2011 XLT SCab 4X4 with the 5.0. One question I have yet to resolve is which rear end ratio to go with. The 3.73 makes the most sense based on past experience but I don't know how tall the 6th gear is in the current truck. I assume quite a bit taller than top gear in my old truck or what would be the point of the extra gears. I am also somewhat concerned about the torque output of the 5.0 in the 2,000 -2,500 rpm range so the slightly lower 3.73 may help in this regard as well. Hopefully Ford will publish a torque curve for the new 5.0 in the near future.

For those who have owned or spent time in more recent trucks with the 6-speed, which rear end ratio would you go with?

Greg

 

Do you tow and if so what are you towing? Are you staying with stock wheels/tires or plus sizing? Lift, drop, or stock height?

 

6th isn't really much taller than 4th in yours, but 1st is considerably lower than your 1st. This makes up for axle ratio quite a bit.

If you want a torque curve as wide as Texas, wait for the Ecoboost.

 

See the ratios here. THe 4.6L 2V has is still using the same ratio 4-spd for comparison.

6th gear is 0.69:1 vs. the 4-spd's 4th gear at 0.70:1. Little difference. So all almost all the benefit is in lower gear for acceleration and smaller gear spacing for less power drop off when shifting. The benefit of a shorter (numerically higher) axle ratio comes main on the highway. If you think 3.55 is enough to keep 6th gear in most of your driving, than it would be fine still.

That said, there has yet to be any comparison showing measurable real world fuel economy differences between 3.55 and 3.73 in an F-150 since 1997. I see no reason not to get the shortest axle ratio possible. I have never regretted it and still wish I had 4.10, maybe 4.56.

 

Go for the 3.73 ratio. Unless you live on flat level ground I have experenced the 3.73s will give better mpg's than the 3.55s.Even on level ground you have to overcome wind resistance.
I once changed the ratio in a police car from 3.43 to 3.73.After the change the mpg was the same but it would run 20 mph faster.Speedometer was corrected.It did have lights on top.Before it did not have the power to overcome the wind resistance making it harder on gas.It was much quicker after the gear change.
I ordered 265/70/17 tires on mine which are tall so I odered 3.73 on mine.With that tire size I wish a 3.91 would be available.

 

I would go 3.73. I wish I had of on my 2009 but I had to take what was available on the lot. If I ever go with tires above 33" I will change my 3.55's for something deep into the 4's.

Depending on the torque curve you may actually get better mileage. The extra snap with the lower gear will always be welcomed.

I think people on here have said there is less than a 200 RPM difference at HWY speeds.

5.0 + 3.73 = fun. Ecoboost + 4.10 = funner

 

Thanks everyone.

So far towing is limited to two dirt bikes in the bed and a couple jet skis on a trailer. I hope to add a travel trailer this coming spring and will weigh in around 4,000 pounds.

Greg

 

4000 pounds is nothing for these trucks.

 

Running the 3.73 now in a FX4 and its great for everything. The Ecoboost with 3.73 will be quite a ride!

 

Go 3.73s for sure. It will give you a little more advantage getting loads up and moving and won't really hurt your MPG that much. I wish I had them in mine, but couldn't get them without the super tow package.

 

Def 3.73's....if you plan on lifting it I would want something in the 4's....I wish Ford would offer the 4.10's from the Raptor in the FX4 models with the locker for those of us who plan on going higher with bigger wheels/tires.

 

Ecoboost has a 0.61 6th gear, found that on this site: http://www.trucktrend.com/features/t...pec/index.html
I want to order one & am also wondering which rear gear. Seems like I read where the 4.10 is available with max tow package?

 

my stx reg cab 4.6 2v has 3.73's. but still seems.... not underpowered but not powerful.

 

I have a 5.4L with 3.73LS and run right around 2000 RPM at 70 MPH with stock tires (265/70R17). I try to avoid driving in town and on the freeway. My gas milage seems to be best around 1500 to 1750 RPM. I plan on taller tires in the distant future. I love the tranny/gear combo though; it's better then anything I've had in the past.

 

4R70W or 4R75 = 2.84, 1.55, 1.00, 0.70
6R80 = 4.17, 2.34, 1.52, 1.14, 0.87, 0.69

4R70W with 5.14 Rear Axle = 14.60 Launch Ratio
6R80 with 3.55 Rear Axle = 14.80 Launch Ratio