I have 315's tires and 3.55 gears. If i change the gears to 4.10 will i have better gas mileage than i have now? Or will 4.56 be better with gas mileage? As of now i get about 11 miles to gallon in city. Which setup is better?

 

Generally speaking, your gas mileage will be worse with 4.10's and worse again with 4.56's. This is because for a given road speed the engine & drivetrain losses will be higher.

In my case, I found that going from 3.55's to 4.10's didn't make a noticable difference in economy (I didn't do a before and after analysis) but it did make a big difference in power.

Ian


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99 Expedition EB
5.4l, 4x4, 4.10 LS
WMS Tube, Bassani Cat Back Exhaust, Superchip Flipchip

 

If yo think about it, 4.10's may give BETTER fuel mileage, particularily in city driving! Simple, really. Lower gear ratio means more torque to the wheels, for the same engine power, which means less lugging the engine. Lugging, or having the engine work below its optimum power band (which is always happening with good sized tires, and only 3.55 gears or less, in my opinion), really sucks gas.

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'97 F-150 4x4 SC SB 4.6L. Riding on Sport King 265/75R16 AT's. Add-a-Leafs & Torsion lift. Side Bars. WMS Intake, TB spacer, and Superchip!

Wish list: 4.10 Gears, Hedman Hedders, 3" body lift, 33x12.5 MT's!!

 

JSL1414,
I think because you have 315 tires your mpg will improve with 4.10's. If you had stock tires then no. The 315's make your truck work harder because you change your gear ratio just by changing tire height. When I put 33's on my truck my power and mpg sucked. Then I put 4.10's in it. The power came back and then some. And my mpg was close to stock. As far as 4.56's, I dont know. I have never gone that big. I think the 4.56's may hurt your mpg but give you a better percieved power increase. The gear change was the best mod that I have done. Also the most expensive, but well worth it. Good luck

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2000 F-150 2wd sport 4.2 V6
XLT, Ext cab, auto transmission

(Performance)
JBA Headers:Jacobs Ignition:K&N:Superchip
Throttle body spacer: Cat back exaust
4.10 gears (had 3.55)

(Appearance)
AR 17x10 Atlas Wheels
Custom Seat Covers: Dash Mat
Floor Mats: Cd player: Pioneer Speakers
Rockford Amp: Truck box: Rhino Liner
Grill Guard: Nerf Bars: Fender flares
Custom graphics: Tail light covers
Vent Visors: Driving Lights
Tinted windows
3 inch spindle lift: 3 inch body lift: lift lips
33/12.5/17 Procomp A/T

 

It appears we have (had) a similar animal. My 4.2 is running 315s on it with the 3:55 Gears. I am considering 4:10s this week and was quoted 550 (w/o Posi). Is that reasonable? Posi would add another 400. I am having difficulty pulling my boat (approx. 2800 lbs.) out of the water on steep ramps. Clutch burning from running RPMs to keep torque up.

 

JSL1414,

I went to 4.10s from 3.55s. My tires are not as tall as yours (see sig) but I get 1 mpg less around town but sure do get where I'm going quicker! Haven't tried highway mileage yet but am taking a trip next week. I'll let you know what it is.

WarEagle

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98 F150 Lariat extended cab, Pacific Green/Silver Frost,
Grey Leather Capt chairs, AM/FM/Cass/6-cd changer,
full tint, color matched bug deflector, vent shades,
A.R.E. hard bed cover, Ultra type 50 polished wheels,
BF Goodrich 315 55R x 16 Sport Truck Radial T/As, 4.6L,
AT, Towing Package, Airaid, Superchip, JBA headers,Flowmaster dual
exhaust, Flowmaster 50 series muffler, 4.10 gears

 

I was wondering what kind of RPM difference you guys had going from 3.55 to 4.10 gears? I'm looking into the same swap myself.

------------------
97 f150 X-CAB SB 4X ORP
Loaded
Supercharged 5.4 (Magnacharger)
with a Superchip
K&N air filter and Dual exhaust complete the package.

 

Sheen,

At 70 mph I am turning 2300 RPM. Checked my milage today ang got 15.1 in town.

WarEagle

------------------
98 F150 Lariat extended cab, Pacific Green/Silver Frost,
Grey Leather Capt chairs, AM/FM/Cass/6-cd changer,
full tint, color matched bug deflector, vent shades,
A.R.E. hard bed cover, Ultra type 50 polished wheels,
BF Goodrich 315 55R x 16 Sport Truck Radial T/As, 4.6L,
AT, Towing Package, Airaid, Superchip, JBA headers,Flowmaster dual
exhaust, Flowmaster 50 series muffler, 4.10 gears

 

WarEagle,

Thanks for the reply, I'm currently turning 2250 @ 80MPH. I'm running the 265 70 17's with 3.55 gears.
------------------
97 f150 X-CAB SB 4X ORP
Loaded
Supercharged 5.4 (Magnacharger)
with a Superchip
K&N air filter and Dual exhaust complete the package.




[This message has been edited by sheen (edited 05-03-2001).]

 

I just fill up my tank today and with about 70 miles of very high speed driving and around town, I got just a fraction over 17 mpg. Normally around town, getting on it a lot, I get just over 15 mpg.

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"The Beast" 98 White 4.6 Triton STX (It's not an STX anymore) Flareside,Class III hitch.
Appearance Mods: Blue Cobra Stripes, Euro Lid by Astro, Bed Rug, Fiero Wing, Air Dam,Ground Force 2-4 Drop,Custom MB Phantom Wheels,clear corner lenses,monster battery terminals, Custom Ford Racing, Leather Seats.

Stereo Mods: MTX Dual Sub Box with 2 10 inch Polks, 4 Polk Speakers, MTX 102 Amp with a Pioneer FH-P4400 CD, Cassette Head Unit

Performance Mods: 96 Crown Victoria Electric Fan Mod, Custom Programmed Super Chip,BBK 75mm TB, Pro M 80mm MAF,Custom Welded Powder Coated Intake Tube,Pillar Pod w/ boost and trans temp,Jacobs DIS Ignition,Art Carr 2400 Stall Performance Transmission,4:10 gears with Auburn Pro Limited Slip,TA Performance Rear End Girdle, Cal Trac Traction Bars, Jet coated JBA stainless headers, custom Y pipe after the Cats, Magna Flow Muffler with Stainless Duals and of course fully Blown by Magnacharger![img] [URL=http://www.zing.com/picture/p8a83f7018b9830708a50753319d962de/fe8bb1f2.jpg[/img]
Best 1/4 So Far 15.117 @ 89.05
Best 60' 2.137
[URL=http://www.zing.com/album/?id=4293450711



[This message has been edited by Flats Man (edited 05-11-2001).]

 

3.08 gears and 4.6 70 miles an hour rpm 1800
22 miles per gallon. sweet

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1997 F-150 XLT 4.6 REGULAR CAB, FLARESIDE PACIFIC CLEARCOAT GREEN 5-SPEED. WESTIN NERF BARS, POWER EVERYTHING,BUG SHIELD, EX-TANG SOFT COVER, BED LINER(FORD).