I have 3.55s on my '05 4.6 and want to go 4.10s for the extra get up and go. Is it true that with the gear swap I should get better gas mileage (if I keep my foot out of it and obey the speed limit)? I figure the engine would simply have to work less to get up to speed. Can anyone let me know if this is correct? thankyou

 

This is correct to a point. Alot of it depends on tire size. With stocl tires 4.10 gearing will probably help your city mileage but hurt your highway milage (70+ mph)

but overall it would help.

 

I can say this ,,,dont' go to 373's!!!! and 456's are prob. too much. Like trimble said, tire size has a lot to do with it, and city vs hwy. driving. 410's i think is a perfect happy medium , unless your going to 35's or larger. Yes, the engine/tranny has to work less moving that beast around in town, and mileage may suffer just a little on hwy. I have the 05 4.6 355 (or did have), its a absolute dog (scab 6.5 box). it bogs down just pulling my 14' empty utility trailer that weighs around 1000 lbs. I have 373's now only because i switched to the 975 pumkin, I cannot tell the diff. Even at 70 mph, i'm still at just a tad under 2 grand rpm. This spring i'm going for 411's. (w/stock tires that will be right on i think) Either Richmond, Yukon, or Ford racing, but not Motive. My .02 worth....rossford

 

You would get
better acceleration and performance with the stock tires. Maybe 1 mpg less on the highway. Would be a good move if your going with larger tires or pull a trailer on a regular basis. A 4.10 gear may be better for these heavy truck's in my opinion.

 

I think these trucks especially 04-08 should have came with either 3.73 or 4.10 nothing taller. But thats just me.

If you plan on towing ALOT and are only 2wd id take the step up to 4.30's
but thats only if you tow ALOT or never get on the highway.

 

I have 20" ROUSH wheels on street tires (not huge off roaders). i would say these arn't the stock config so how would the 4.10s help/hurt my gas mileage (obviously keeping my foot out of it and obeying freeway speed limits)? maybe this info might help

 

I also think these trucks should have come with bigger tires. Another American brand truck that my buddy just bought came with 33" tires.

 

It's the diameter of the tires that make a difference not the wheel diameter. A truck with a 4.10 rear will accelerate quicker than say a truck with a 3.55 or 3.73 rear from 0-60 mph. Also lower gears will move these heavy truck's from a dead stop easier and have less stress on the engine. At highway speed's the overdrive in the tranny will bring the rpm's down to a managable level to still get decent gas mileage. Year's ago pickup's alway's had mainly small engines with 4.10 or lower gear's in the rear end's and no overdrive in the tranny's untill the early 80's. My first F-150 was a 1984 with a 302 carb. engine, C-6 trans. and who know's what gear ratio and I was lucky to get 14mpg top's. I had 2 gas tank's and needed both of them! These truck's have come a long way to improve fuel mileage.

 

My dad has an '04 (new style) with the heavy duty payload package (7 lug) and stock comes with 4.10's. If you keep your foot out of it on the highway, you won't notice a difference MPG wise. To be honest, I think it gets the same MPG's as my truck with the 3.55's.

 

The 4.10's on the HD package was nice, now they show 3.73's with the HD package on the '09's.

 

^^^ correct ford dropped 4.10s from their lineup for 2009


Yes theoretically you will get better mileage city, and slightly worse on the highway

 

why does it seem like everyone bashes the motive gears? are they prone to whine? in my searches i've heard good things about ford racing and yukon. what are some good places to order the gears at (low price, good rep., etc) and what should I expect the price range to be on just the rear install? thank you

 

FWIW, FMS gears are now "outsourced" and I've heard plenty of complaints about gear whine from them now. Shops now recommend Yukon and Motive.

 

Correction: i have 3.73 gears. found the original window sticker in the glove box tonight.
So if 3.73 feels really weak to me how much of a difference will i feel with the 4.10s? I guess what I'm asking is how much of a torque increase would it feel like going from 3.73 to 4.10 or even 4.30? wow i just figured i had 3.55 because this 4.6 is such a dog.

 

Its the motor pull it out & replace with a 5.4 motor= problem solve.