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what should I do about gear ratio

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by nc87k5, Sep 25, 2003.

  1. nc87k5

    nc87k5 3/4 ton status

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    I found a link from here that will give you your true gear ratio when you change your OE tire size. For mine, a 3.08 with the 32's on it is now a 2.73. would i get better gas mileage with some 3.73's or worse? /forums/images/graemlins/k5.gif
     
  2. big pappa b

    big pappa b 3/4 ton status

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  3. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    actually you would get better mileage /forums/images/graemlins/thumb.gif
     
  4. doctor4x4

    doctor4x4 1/2 ton status

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    I agree with Mud on this 1 as your motor is in th power band and therefore more effecient
    besides real world experience has showed - taught me
    3:73 with 33" tires with a good stock or slightly modifed sbc will produce up to 15 - 18 mpg highway and 12-15 ish city
     
  5. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    more like 8 in town and 14 on the highway for me but my foot is always on the gas /forums/images/graemlins/blush.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
     
  6. nc87k5

    nc87k5 3/4 ton status

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    hellava site better than mine, I'm getting 8-10 miles to the gallon now. /forums/images/graemlins/eek.gif
     
  7. big pappa b

    big pappa b 3/4 ton status

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    /forums/images/graemlins/frown.gif /forums/images/graemlins/frown.gif Too quick to jump on the higher gear ratio = less mileage bandwagon
     
  8. heavy4x4

    heavy4x4 1/2 ton status

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    Ah, the infamous "what ratio will get better mileage."

    Two trains of thought and two "correct" answers.

    1) If you run too low (numerically high) of a gear ratio for the size of tire you have, you'll run higher rpms on the freeway and cruising, thus consume more fuel.

    2) However, I was running with 33's with stock 3.42s and got worse mileage than when the vehicle had 29's. So, this was a case of the gear ratio being too high (numerically low) for the tire size and I got worse mileage. We're talking like 2mpg difference.

    People can argue all they want, but there's no denying real-world experience and math.

    Basically, it's a fine balancing act between getting a ratio that doesn't increase your cruising rpms much and one that keeps your engine from lugging while cruising at lower rpms.
    If you have a manual tranny, you can pick the right gear for the speed, so there's more fudging in that too.

    Overall, just pick a gear that's close to what you need. Doesn't matter if it's one step higher or one step lower, your gas mileage is gonna suck anyway.

    (Now, if you're worried about performance issues, that's another topic...that has a lot to do with rpms and in that case you'll want to be more picky about the gear you choose.)
     
  9. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    if your going to re gear and ever plan on going up to say 36's then get 4:10's now if you don't ever plan on going more than 33's maybe 34's go with 3:73's /forums/images/graemlins/thumb.gif
     

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