my 99 eclb is all stock with 4.10s and has 134k,it gets 10 with a good tailwind

 

how much does the 4:10 gears increase mpg? I do ALOT of towing so they might be a good idea.

 

I get around 10mpg city and around 15 highway. it doesnt matter if I have my 285's or 305 tires on. All in a regular cab 4X4 with 4:10's.

 

Did you correct your speedometer for the bigger tires? Bigger tires will slow down your stock speed/odometer reading giving a inaccurate low mpg reading.

 

I get 11 city 14 Hwy with my 07 3V. I did replace the stock 17 inch tires with 18 inch, would that drastically alter my speedometer? How do I re-calibrate for the difference? Thanks.

3.73 gears

 

Also....I have 4:30 gears

 

Not sure about Long Haul but my 35's actually corrected my speedometer it was fast from the factory so the big tires slowed it down to be spot on up until like 50 mph then it varies by about 1-2 mph from there up for some reason.

 

my mods listed in the sig i get 10.29MPG mostly all city driving and ever weekend i have a 26mile trip (one way) to pick up my daughter. On the highway with my setup doing 65mph gets me the best highway MPG, you have to understand you have a nearly 7k truck that's HUGE most come with entirely too small 3.73 gears then add in a 330cubic inch 260HP motor thats JUST OK 10-12mpg is all your gonna get. BUT even if you sell her and go buy a Chevy/GMC or Dodge Heavy Duty with a gas motor THEY ALSO ONLY GET BETWEEN 10-12MPG. Ive never driven a HD GM truck but i have raced three that all had the 6.0 Vortec and my little engine that could somehow won ever time, I never driven or raced a Dodge so i cant say how they perform...... Ive never towed with either but from what i was told from guys who own 6.0 HD Chevy's that once they get to around 6-7k trailer weights and above they too strain and struggle just like the 5.4 motors....

 

my truck was a 3.73 geared slug from jump street and after the first few weeks I knew I hated the thing, jump forward 2 1/2 years and I had enough and had 4.30 gears installed. It doesn't have diesel low end grunt but the 4.30 really made me like the 5.4, it tows SO MUCH better now ans getting a load moving you really see and feel the difference. Cant say if I gained or lost MPG with the 4.30 since I don't have the MPG records anymore but I say i gained because I no longer have to plant my foot to get a load moving so yea GAIN

 

Nope. I have a 3v, 4.10 gears and 285 tires. I get 9-10 suburbs and the best ever of 11.8 on a highway trip. I'm 5 star tuned so the gas pedal throttle curve has been steepend a lot. (3v motor has drive by wire) and I drive to keep up with quick traffic from a stop.

 

No I didn't never even thought of that.....Thanks

I'll use the GPS to check mileage for the next fill..

 

With 4.30 gears and 255 85r16 tires my speedo is dead on, going from the SCT paperweight and all the speed radar signs around my area

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