Late September snow.. Yikes Where are you located?

 

can some body help explain to me how to find out what kind of gears/rear end I have. and what is the better.

 

bryan,

The numerically higher stock gear, the better. Check your axle code on the river's doro sticker.

19 = 3.55 open
H9 = 3.55 LSD
26 = 3.73 open
B6 = 3.73 LSD
27 = 3.31 open
18 = 3.08 open
25 = 4.10 open
B5 = 4.10 LSD

 

That's not necessarliy true for everyone. Me personally, I like my 3.73s even though I run the highways a lot and would probably be fine with 3.55s and would probably save a little gas.

Generally speaking most people benefit from numerically higher gears since it usually helps city mileage and gives your truck better acceleration and higher towng capcity BUT people who drive the highway a lot are better off with numerically lower gears to reduce the cruising rpms.

 

Subjective terms. There has been no evidence that 3.73 consistently uses more fuel than 3.55. Changing the engine speed at say 70mph by 100rpm will not change the fuel map much. In fact, it could be worse if the engine no longer has the torque (by lower engine speed and taller gearing) to no longer hold top gear for as many hills/inclines.

 

our 09 F-150 4.6 SuperCrew 5.5' bed 4x4s w/ 3.73s XLT package are getting 18-19, several different drivers, several different areas. Younger guys are getting 18 older are getting 19 to 20.

 

I have a 09 xlt chrome package, 5.4 with tow package, with 20" procomp wheels adn 305/55/20 extreme AT's, a 2" leveling kit and tonneau cover. with a good tail wind I might get 15mpg, but right now averaging 14.3... Needless to say I am a little disapointed, but this is the only thing I am disapointed about.. almost. (I do wish I had the cup holders I had in my 02 superduty)
I was thinking about getting an intake and exhaust set up to hopefully improve on my mileage a bit, but who knows.

 

gears?? if your running 3.55s or worse i can see that. are you calculating for the tire size change too?

 

My 09 SuperCrew 5.5' bed 4x4, 3.73s, 5.4, factory 20" wheels, with 6k on the clock, has gotten a constant 15.5 on mixed driving.

 

So - I was thinking of ordering my 2010 Lariat screw 4x4 with the 3.55LS gears. I do almost entirely city driving - are you all saying here that I'd get better mileage with the 3.73LS gears?

 

You aren't going to notice much if any difference in mileage between the two ratios. Driving style is going to matter more than gear ratio. The only thing I will say is that if your going to be towing something big then you might select the 3.73LS.

 

Man, I'm way out of the average. Although I only have about 500 miles on my 2010 4X4 Lariat, my last trip, mostly interstate averaged 15.8 MPG. Kind of disappointing because experience tells me it's not going to get a huge difference after 5000 miles or so. The same trip on my 04 4x4 would have been 18-19 MPG. I had a soft access bed cover on it and just maybe that helped some, but I doubt it. But the main thing is, I don't care! The ride, comfort, high tech features and a safe feeling is worth it to me. I don't want to get out of it, sick I'll tell ya.

 

My 2009 SC, 5.4L, 3.73 FX4 has 21,14x miles on it (bought it new first week in May). Laredo soft cover, no lift or big tires.

Overall calculated fuel economy 18.6 mpg (1137.1 gallons purchased)
Top tank 21.3 mpg - (Iowa to Kansas trip in rain, avg speed 57.1mph)
Worst tank 15.9 mpg - (Iowa to Chicago, avg. speed 71.3 mph)

I drive Iowa, Missouri, Nebraska, and Kansas for work. I average 60-65k per year, and keep my trucks 5 years. Traded 2004 F-150 SC (similar equipped) with 318,4xx miles for $8400.

2004 doing the same job averaged 15.3mpg over its life. Based on my personal driving requirements, the 2009 will save me approximately $1700 per year in fuel costs. The 2004 had just over $57k in fuel run through it.
Total operating cost of the 2004 was 0.294 cents per mile of operation. I pay cash for new vehicles, so I don't assume cost of money (interest lost on the investment) in the calculations.

Not hauling anything but customers, mainly highway driving of course.

IowaAndy

PS - I'm an engineer if my data doesn't indicate it

 

MrFission, you gotta pay to play. The playground you are in is the large/heavy wheels and tires. You do need to correct for the large tires, but that will mean less than 1mpg increase. What size tires were stock? (hint, check fuel filler door or driver's door sticker)

fjc, if you want more than 1200 pounds of available payload, get the max towing package.

Wrench, your FE will improve over the next 5k miles.

 

Here is my mileage on my 09 Screw FX4, 5.4L 3.73 rear.
___________Odometer/Gallons/MPG
8/11/2009 230
8/12/2009 299------5.28-----13.07 Reg
8/13/2009 501------12.16----16.61 Reg
8/18/2009 742------18-------13.39 Reg
8/24/2009 967------16.9-----13.31 Reg
9/2/2009 1194------17.69----12.83 E85
9/8/2009 1386------16.67----11.52 E85
9/11/2009 1536-----12.75----11.76 E85
9/20/2009 1807-----22.87----11.85 E85
9/25/2009 2065-----23.63----10.92 E85
10/2/2009 2339-----23.28----11.77 E85

Overall average is 13.45 mpg