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  1. #1

    Exclamation Better gas economy

    hello gents,
    i have 99 burb with a 7.4 vortec, 4.10 gears and 4x4. that was getting 14 mpg doing 65mph which i know is good for a big block, i really like the the tank but, has anyone change the rear in gearing to get better mpg. i dont pull heavy load with it, so the 4.10 gear are really not needed or is it.. need help answering the question, has anyone one changed to a 3.73 or a 3.42 and what was the improvement in mpg.. this is my wife grocery getter... thanks for the advise...Cody

  2. #2

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    Welcome to the site...sorry I cannot help you with your gearing question...I went the opposite direction when I re-geared.

    Bobby - North Carolina
    2008 4x4 5.3L V8
    6" Suspension Lift and 1.5" Body Lift
    20x9 Ballistic Jesters w/35" Toyo Open Country MT's & 1.5" rear wheel spacers
    4:56 Yukon Gears
    Hypertech Speedometer Calibrator
    Baja style bed mount spare tire carrier
    Flowmaster 40 series dual exhaust
    Recon Smoked LED tails/3rd brake lights/black projectors w/switchback LED's in the corners
    N-Fab Nerf Steps
    K&N CAI
    No Fear Pedals
    Tint, Line-X bedliner, Window visors, Rear wheel well liners
    Painted front grill, bow ties and door badges, de-"lettered" tailgate
    Powder coated front and rear bumpers

  3. #3
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    Eddie Z71's Avatar
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    Hi, and welcome to the site! Hope a member can help you with your question that has done this before!
    Eddie , 2000 Chevy Tahoe Z71 (old style)

  4. #4

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    Welcome to the site! If you don't need the gears for towing, the 3:73s should be fine. I don't know about the 3:42s though. Good luck!


    2010 Z/71 Colorado C/C
    Black 4X4 w/5.3L V8
    ===============
    2007 Winnebago Adventurer
    w/8.1L Chevy & Allison 6spd.
    Canyon Lake, Texas

  5. #5

    Default

    thanks guys
    im am wanting to know if it is worth it to change because the cost of the gears and labor. you know cost vs. monies saved in fuel...

  6. #6
    Jr. Engineer lsutoms's Avatar
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    Quote Originally Posted by cowboycody85 View Post
    thanks guys
    im am wanting to know if it is worth it to change because the cost of the gears and labor. you know cost vs. monies saved in fuel...

    +1! gears run about $800 an axle.... prob better to stay with what u got!

  7. #7

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    Welcome To The Site, Hope To See You Around

    '96 K1500, 5.7
    6" RCD
    35" Toyo M/T On 16" Black Raceline Raptors
    4.56 Yukon Gears w/ TruTrac Rear
    S&B CAI
    Dual Flowmaster 40's
    Camo Wet Okoles
    Line-X Bedliner
    De-Badged


    NW BlackDiamond Edition

  8. #8

    Default

    You would have to do both diffs I would look at doing a few breathing mods that might pick it up as well as a set of good rubber to decrease rolling resistance.I found that keeping the tach 2000 and below starting out gives me the best milage
    Last edited by azdrtdog; 01-23-2010 at 11:07 AM.

    99 tahoe 2 dr. 4x4 7.4 4L80-e NP246, SAS, dana 60 hp, sterling 10.5 rear, gibson headers, and alot of tricks of the trade !!!!!!IF YOU'RE NOT CHEATING YOUR NOT TRYING!!!!!!!!

  9. #9

    Cool Better gas economy

    It will take alot of miles to recoup the cost of the gear changes. Id keep what you have . I would run sythnetic fluids in the truck, engine, tranny,transfer case and the axles.

  10. #10

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    i would start with what siveradeo said start with the fluids, i use all syn also up grade your air intake i use afram air hog on my v8 jeep and also there is a site called racingguys.com you can et a niced polished intake with a re useable filter for about 65 dollars put one on my sons 5.7 k2500 4x4 they all seem to add about 1/2 mpg gallon up here in minnesota we have so many clean burn fules that it hurts your milelage. i did find filling up once a awhile with the mid level gs 89 oct helps also ..

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