https://www.f150online.com/forums/ar...wap-notes.html

 

If there was still the option of an inline 6 I'd jump on that like a Catholic priest to an altar boy. Torque galore, not much for speed. I could justify it being slow at that point

 

fyi adding RPM does not automatically reduce gas milage......

YES I SAID IT.......
There are many variable at play here. RPM, Torque, efficiency. That being said turning 1600 rpm may actually net you WORSE milage than turning 2800 rpm....because you are knee deep in an under geared slug as opposed to in the TARGET range of torque RPM.... requiring LES throttle changes to maintain XXX MPH..(or head wind, 1% grade , changing lanes...farting forward...etc)

BTW.... 2 wheel 4x4 ....gear...what are we working with here....it will keep out the riff-raff..

 

She's a 2wd 4.6, 4r70w out of an 01 expedition, 3.55 gearing. Not much to work with. Thinking of trying to find a modified transmission to get me another forward gear to improve gas mileage

 

I can attest to this with my V6.

When I had 3.31 for the first year or so I owned it, fuel mileage was terrible.

I changed it out to 4.10 and even though the engine is running faster, it's way more efficient. I've been able to achieve 18-22mpg on flat surfaces cruising at 50 mph. Truck is very happy at that speed.

Plus it helped 1st gear towing and starting. I let off on the clutch and the truck won't even stall at idle. Very nice for creeping.

Mind you, I'm running standard size tires. They are knobby, but they are standard size.

 

Ooohh! You'll burn for that one! :-)

 

Considering the other things I say on a regular basis im not going to hell. Satan doesn't even want me anymore

 

Supercharger

 

Might recommend using your "O.D. lockout" button....FIRST. drive a tank of gas WITHOUT OVERDRIVE (every single time you drive it)......just normal driving ...see what if any difference you get in milage (should be a little better! ) with that it will give you a feel of what a GEAR SWAP will feel like WHILE CRUISING.
(I love gears!!!...best tune-up you can do to a vehicle) The acceleration will be drastically changed IN TOWN ....with a gear swap ...but it all depends on what kind of drive you have regularly. Mine is mixed highway/city about 60/40
Gear change = about $600 installed or $350 if you can do it. then $200 to flash the ecm for the proper speedo/shift point fix or $350 for a handheld and you do it yourself (with some tuning abilities) so...$800-$1000
tremendous difference in every driving scenario. (so long as we stay within the 4.6's power rpm range (you don't need 5.13 gears.....nor would 3.73 do much) probably 4.10 gear.
Supercharger .... ...POWER = YES...drivability = YES, reliability =YES (but they do require maintenence and have a LIFE CYCLE)
noticeable change throughout the entire driving range.... PRICE $2500-3000 if all goes well and depends on how much work YOU can do expect $1200 for install

so the same old ? comes up AGAIN
How fast can you afford to go?

Hot rod mantra: Take your expected budget to complete the task......now double it and you will be very close!

 

Go with the superchips.best cheap power booster.

 

I know My experience is different then others but I have a 01 expedition with a 4r70w and 3.31 gears running a factory lightning height tire which I believe is considered
a 28.5 inch tire or 3% smaller then stock and the only time mine needs to down shift is on a large hill is towards the end of the climb. I haven't done any mods to it but
suspension and exterior and interior. If I went to a 3.55 it would be a improvement and 3.73 would be night and day. People may say 3% isn't much but at 2000 RPM's 3%
makes a difference. The same would go for you. Mechanical advantage and keeping your highway RPM's between 2000-2200 will improve your mileage alot. Most boxed
tunes are not a good Idea because I know first hand that they lean out the fuel trims and screw with timing which is asking for trouble. If you are keeping everything stock
I would work on gearing or tire size to gain the advantage you need. Lifting it, big ars tires, will increase drag that equals crap gas mileage. It will make you feel like you're
driving in a perpetual 50mph headwind.

I will assume we are talking about your Supercrew. With tow package will have 3.73 and without can have either 3.55 or 3.73 but usually 3.55. If you have 3.55's then you would
be extremely pleased with 3.90's provided you are 2wd, because there isn't a reverse cut 3.90 set yet. If you go to a 33 or 35 inch tire you would need to consider
4.10/11 or 4.56. The big thing here is when going down the freeway to be in the powerband but not at 4000 RPM's either.

 

There more in play here than just bad gas mileage. I had an 02 Supercrew with the 4.6 and ran the 265/75/16 tires. I got 17-18 mpgs town driving with it. Jeez, on one trip from Knoxville to South Texas I ran that truck flat on the floor the entire way only lifting long enough to put gas in it and still got 17mpg. There more wrong here than a tired 4.6 and it obviously isn't under the hood.